Golf ball construction

ABSTRACT

The present invention relates to golf balls having a low specific gravity core with specific gravities less than 1.05 and one or more high specific gravity intermediate layers with specific gravities greater than or equal to 1.05. The resulting golf balls exhibit significantly decreased spin and long distance and have the added benefit that the high specific gravity intermediate layer can be easily injection molded around the low specific gravity core.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/593,449, which was filed on Feb. 1, 2012, and is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to golf balls comprising a low specific gravity core, an outer cover layer and one or more high specific gravity intermediate layers.

Description of Related Art

Most modern golf balls can be classified as one-piece, two-piece, three-piece or multi-layered golf balls. One-piece balls are molded from a homogeneous mass of material with a dimple pattern molded thereon. One-piece balls are inexpensive and very durable, but typically do not provide great distance because of relatively high spin and low velocity. Two-piece balls are made by molding a cover around a solid rubber core. These are the most popular types of balls in use today. In attempts to further modify the ball performance, especially in terms of the distance such balls travel, as well as the spin and the feel transmitted to the golfer through the club on striking the ball, the basic two piece ball construction has been further modified by the introduction of additional layers between the core and outer cover layer. If one additional layer is introduced between the core and outer cover layer a so called “three-piece ball” results, if two additional layers are introduced between the core and outer cover layer, a so called “four-piece ball” results, and so on.

Golf ball covers were previously made from balata rubber which was favored by some players because the softness of the cover allowed them to achieve spin rates sufficient to allow more precise control of ball direction and distance, particularly on shorter approach shots. However balata-covered balls, although exhibiting high spin and soft feel, were often deficient in terms of the durability of the cover which had a propensity to shear and also the velocity of the ball when it leaves the club face (which in turn affects the distance the ball travels). In addition, increased spin on the ball when struck by a driver or long to mid iron can be detrimental to distance as an increase in the amount of side spin can, depending on its direction, cause the ball trajectory to veer left (hook) or right (slice).

It is well known that the total weight of the ball has to conform to the weight limit set by the United States Golf Association (“USGA”). However, changing the distribution of the weight or mass of the ball either toward the center of the ball or toward the outer surface of the ball changes the dynamic characteristics of the ball at impact and in flight. If the density is shifted or distributed outward from the central core, the initial spin rate of the ball as it leaves the golf club would decrease which is an important factor in improving distance for a given golf ball design.

Thus it would be useful to develop golf ball constructions and methods for producing them which can minimize spin on impact while still maintaining other important parameters of golf ball performance.

SUMMARY

This invention pertains to a golf ball which includes a core having a specific gravity of less than 1.05, one or more intermediate layers having a specific gravity of greater than or equal to 1.05, and an outer cover layer.

In another aspect, the invention pertains to a three piece golf ball having only a core, an intermediate layer and an outer cover layer. The core has a specific gravity of less than or equal to 0.85 and includes natural cork or a closed cell foam having a density from about 0.2 to about 1.04 g/cm³ and a closed cell content of greater than or equal 70% (as measured according to according ASTM D2856-94) or a mixture of both. The intermediate layer has a thickness from about 0.010 to about 0.400 inches and a Shore D hardness (as measured on the ball) of greater than about 25, and includes a polyalkenamer having a trans-content from about 40 to about 95%; a cis-content from about 5 to about 60%; a melting point of greater than about 15° C.; a viscosity of less than about 5,000 Pa-sec (as measured using a Dynamic Mechanical Analyzer and ASTM D4440 at 200° C.); and a storage modulus (G′) of greater than about 1×1b 0 ⁷ dyn/cm² (as measured using a Dynamic Mechanical Analyzer and ASTM D4065, at 25° C., and 1 Hz). The outer cover layer has a thickness from about 0.015 to about 0.100 inches and a Shore D hardness as measured on the ball of from about 30 to about 75, and includes one or more of the following polymers, ionomers, thermoset polyureas, thermoset polyurethanes, thermoplastic polyurethanes, thermoplastic polyureas, a multicomponent blend composition (“MCBC”) comprising (A) a block copolymer; and (B) one or more acidic polymers; and (C) one or more basic metal salts present in an amount to neutralize at greater than or equal to about 30 percent of the acid groups of Component (B).

In another aspect, the invention pertains to a four piece golf ball having only a core, an inner intermediate layer, an outer intermediate layer and an outer cover layer. The core has a specific gravity of less than or equal to 0.85 and includes natural cork or a closed cell foam having a density from about 0.2 to about 1.04 g/cm³ and a closed cell content of greater than or equal 70% (as measured according to according ASTM D2856-94) or a mixture of both. The inner intermediate layer has a thickness from about 0.010 to about 0.400 inches and a Shore D hardness (as measured on the ball) of greater than about 25, and includes a polyalkenamer having a trans-content from about 40 to about 95%; a cis-content from about 5 to about 60%; a melting point of greater than about 15° C.; a viscosity of less than about 5,000 Pa-sec (as measured using a Dynamic Mechanical Analyzer and ASTM D4440 at 200° C.); and a storage modulus (G′) of greater than about 1×10⁷ dyn/cm² (as measured using a Dynamic Mechanical Analyzer and ASTM D4065, at 25° C., and 1 Hz). The outer intermediate layer has a thickness from about 0.010 to about 0.400 inches and a Shore D hardness as measured on the ball of greater than about 25. The outer cover layer has a thickness from about 0.015 to about 0.100 inches and a Shore D hardness as measured on the ball of from about 30 to about 75, and includes one or more of the following polymers, ionomers, thermoset polyureas, thermoset polyurethanes, thermoplastic polyurethanes, thermoplastic polyureas , a multicomponent blend composition (“MCBC”) comprising (A) a block copolymer; and (B) one or more acidic polymers; and (C) one or more basic metal salts present in an amount to neutralize at greater than or equal to about 30 percent of the acid groups of Component (B).

In another aspect, the invention pertains to a five piece golf ball having only a core, an inner intermediate layer, an intermediate intermediate layer, an outer intermediate layer and an outer cover layer. The core has a specific gravity of less than or equal to 0.85 and includes natural cork or a closed cell foam having a density from about 0.2 to about 1.04 g/cm³ and a closed cell content of greater than or equal 70% (as measured according to according ASTM D2856-94) or a mixture of both. The inner intermediate layer has a thickness from about 0.010 to about 0.400 inches and a Shore D hardness (as measured on the ball) of greater than about 25, and includes a polyalkenamer having a trans-content from about 40 to about 95%; a cis-content from about 5 to about 60%; a melting point of greater than about 15° C.; a viscosity of less than about 5,000 Pa-sec (as measured using a Dynamic Mechanical Analyzer and ASTM D4440 at 200° C.); and a storage modulus (G′) of greater than about 1×10⁷ dyn/cm² (as measured using a Dynamic Mechanical Analyzer and ASTM D4065, at 25° C., and 1 Hz). The intermediate and outer intermediate layers have a thickness from about 0.010 to about 0.400 inches and a Shore D hardness as measured on the ball of greater than about 25. The outer cover layer has a thickness from about 0.015 to about 0.100 inches and a

Shore D hardness as measured on the ball of from about 30 to about 75, and includes one or more of the following polymers, ionomers, thermoset polyureas, thermoset polyurethanes, thermoplastic polyurethanes, thermoplastic polyureas , a multicomponent blend composition (“MCBC”) comprising (A) a block copolymer; and (B) one or more acidic polymers; and (C) one or more basic metal salts present in an amount to neutralize at greater than or equal to about 30 percent of the acid groups of Component (B).

The foregoing and other objects, features, and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a three-piece golf ball 1 comprising a solid center or core 2, an intermediate layer 3, and an outer cover layer 4.

FIG. 2 illustrates a four-piece golf ball 1 comprising a core 2, and an outer cover layer 5. an inner intermediate layer 3, and an outer intermediate layer 4.

Although FIGS. 1 and 2 illustrate only three- and four-piece golf ball constructions, golf balls of the present invention may comprise from 1 to at least 5 intermediate layer(s), preferably from 1 to 3 intermediate layer(s), more preferably from 1 to 2 intermediate layer(s).

DETAILED DESCRIPTION

Any numerical values recited herein include all values from the lower value to the upper value in increments of one unit provided that there is a separation of at least 2 units between any lower value and any higher value. As an example, if it is stated that the amount of a component or a value of a process variable is from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, it is intended that values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. are expressly enumerated in this specification. For values, which have less than one unit difference, one unit is considered to be 0.1, 0.01, 0.001, or 0.0001 as appropriate. Thus all possible combinations of numerical values between the lowest value and the highest value enumerated herein are said to be expressly stated in this application.

The term “bimodal polymer” refers to a polymer comprising two main fractions and more specifically to the form of the polymers molecular weight distribution curve, i.e., the appearance of the graph of the polymer weight fraction as function of its molecular weight. When the molecular weight distribution curves from these fractions are superimposed into the molecular weight distribution curve for the total resulting polymer product, that curve will show two maxima or at least be distinctly broadened in comparison with the curves for the individual fractions. Such a polymer product is called bimodal. It is to be noted here that also the chemical compositions of the two fractions may be different.

As used herein, the term “block copolymer” is intended to mean a polymer comprising two or more homopolymer subunits linked by covalent bonds. The union of the homopolymer subunits may require an intermediate non-repeating subunit, known as a junction block. Block copolymers with two or three distinct blocks are called diblock copolymers and triblock copolymers, respectively.

As used herein, the term “closed cell foam” is intended to mean a foam which has a closed cell content of greater than or equal to 70%, preferably greater than or equal 80%, more preferably greater than or equal 90%, even more preferably greater than or equal 95%, still more preferably greater than or equal 98%, and most preferably greater than or equal 99%, as measured according to according ASTM D2856-94

The term “core” is intended to mean the unitary center of a golf ball.

The term “cover layer” is intended to mean the outermost layer of the golf ball. The term “outer cover layer” as used herein is used interchangeably with the term “cover layer” and is the layer that is directly in contact with paint and/or ink on the surface of the golf ball.

The term “fiber” as used herein is a general term for which the definition given in Engineered Materials Handbook, Vol. 2, “Engineering Plastics”, published by A.S.M. International, Metals Park, Ohio, USA, is relied upon to refer to filamentary materials with a finite length that is at least 100 times its diameter, which is typically 0.10 to 0.13 mm (0.004 to 0. 005 in.). Fibers can be continuous or specific short lengths (discontinuous), normally no less than 3.2 mm (¼ in.). Although fibers according to this definition are preferred, fiber segments, i.e., parts of fibers having lengths less than the aforementioned are also considered to be encompassed by the invention. Thus, the terms “fibers” and “fiber segments” are used herein. In the claims appearing at the end of this disclosure in particular, the expression “fibers or fiber segments” and “fiber elements” are used to encompass both fibers and fiber segments.

The term “hydrocarbyl” is intended to mean any aliphatic, cycloaliphatic, aromatic, aryl substituted aliphatic, aryl substituted cycloaliphatic, aliphatic substituted aromatic, or cycloaliphatic substituted aromatic groups. The aliphatic or cycloaliphatic groups are preferably saturated. Likewise, the term “hydrocarbyloxy” means a hydrocarbyl group having an oxygen linkage between it and the carbon atom to which it is attached.

The term “intermediate layer” may be used interchangeably herein with the terms “mantle layer” and is intended to mean any layer(s) in a golf ball disposed between the core and the outer cover layer. Should a ball have more than one intermediate layer, these may be distinguished as “inner intermediate layer ” or “inner mantle layer” which terms may be used interchangeably to refer to the intermediate layer nearest the core and furthest from the outer cover, as opposed to the “outer intermediate layer” or “outer mantle layer” which terms may also be used interchangeably to refer to the intermediate layer furthest from the core and closest to the outer cover, and if there are three intermediate layers, these may be further distinguished as “inner intermediate layer”, “outer intermediate layer” and “intermediate intermediate layer” or “inner mantle layer”, “outer mantle layer” and “intermediate mantle layer” which terms may respectively also be used interchangeably.

As used herein, “high specific gravity” includes specific gravities of greater than or equal to 1.05, preferably greater than or equal to 1.10, more preferably greater than or equal to 1.12, and even more preferably greater than or equal to 1.15.

As used herein, “low specific gravity” includes specific gravities of less than 1.05, preferably less than or equal to 1.00, more preferably less than or equal to 0.90, and even more preferably less than or equal to 0.80.

As used herein, the term “injection moldable” as applied to the polyalkenamer rubber compositions used as described herein refers to a material amenable to use in injection molding apparatus designed for use with typical thermoplastic resins. In one example, the term injection moldable composition as applied to the highly filled uncrosslinked polyalkenamer rubber compositions used in the present disclosure means compositions having a viscosity using a Dynamic Mechanical Analyzer (DMA) and ASTM D4440 at 200° C. of less than about 5,000 Pa-sec, preferably less than about 3,000 Pa-sec, more preferably less than about 2,000 Pa-sec and even more preferably less than about 1,000 Pa-sec. and a storage modulus (G′) measured using a Dynamic Mechanical Analyzer (DMA) and ASTM D4065, and ASTM D4440, at 25° C., and 1 Hz of greater than about 1×10⁷ dyn/cm², preferably greater than about 1.5×10⁷ dyn/cm² more preferably greater than about 1×10⁸ dyn/cm², and most preferably greater than about 2×10⁸ dyn/cm².

The term “(meth)acrylic acid copolymers” is intended to mean copolymers of methacrylic acid and/or acrylic acid.

The term “(meth)acrylate” is intended to mean an ester of methacrylic acid and/or acrylic acid.

The term “partially neutralized” is intended to mean an ionomer with a degree of neutralization of less than 100 percent. The term “highly neutralized” is intended to mean an ionomer with a degree of neutralization of greater than 50 percent. The term “fully neutralized” is intended to mean an ionomer with a degree of neutralization of 100 percent.

The term “prepolymer” as used herein is intended to mean any polymeric material that can be further processed to form a final polymer material of a manufactured golf ball, such as, by way of example and not limitation, a polymerized or partially polymerized material that can undergo additional processing, such as crosslinking.

The term “sports equipment” refers to any item of sports equipment such as sports clothing, boots, sneakers, clogs, sandals, slip on sandals and shoes, golf shoes, tennis shoes, running shoes, athletic shoes, hiking shoes, skis, ski masks, ski boots, cycling shoes, soccer boots, golf clubs, golf bags, and the like.

The term “thermoplastic” as used herein is intended to mean a material that is capable of softening or melting when heated and of hardening again when cooled. Thermoplastic polymer chains often are not cross-linked or are lightly crosslinked using a chain extender, but the term “thermoplastic” as used herein may refer to materials that initially act as thermoplastics, such as during an initial extrusion process or injection molding process, but which also may be crosslinked, such as during a compression molding step to form a final structure.

The term “thermoset” as used herein is intended to mean a material that crosslinks or cures via interaction with as crosslinking or curing agent. Crosslinking may be induced by energy, such as heat (generally above 200° C.), through a chemical reaction (by reaction with a curing agent), or by irradiation. The resulting composition remains rigid when set, and does not soften with heating. Thermosets have this property because the long-chain polymer molecules cross-link with each other to give a rigid structure. A thermoset material cannot be melted and re-molded after it is cured. Thus thermosets do not lend themselves to recycling unlike thermoplastics, which can be melted and re-molded.

The term “thermoplastic polyurethane” as used herein is intended to mean a material prepared by reaction of a prepared by reaction of a diisocyanate with a polyol, and optionally addition of a chain extender.

The term “thermoplastic polyurea” as used herein is intended to mean a material prepared by reaction of a prepared by reaction of a diisocyanate with a polyamine, with optionally addition of a chain extender.

The term “thermoset polyurethane” as used herein is intended to mean a material prepared by reaction of a diisocyanate with a polyol (or a prepolymer of the two), and a curing agent.

The term “thermoset polyurea” as used herein is intended to mean a material prepared by reaction of a diisocyanate with a polyamine (or a prepolymer of the two) and a curing agent.

The term “unimodal polymer” refers to a polymer comprising one main fraction and more specifically to the form of the polymers molecular weight distribution curve, i.e., the molecular weight distribution curve for the total polymer product shows only a single maximum.

The term “urethane prepolymer” as used herein is intended to mean the reaction product of diisocyanate and a polyol.

The term “urea prepolymer” as used herein is intended to mean the reaction product of a diisocyanate and a polyamine.

The tem,. “zwitterion” as used herein is intended to mean a form of the compound having both an amine group and carboxylic acid group, where both are charged and where the net charge on the compound is neutral.

The present invention can be used in forming golf balls of any desired size. “The Rules of Golf” by the USGA dictate that the size of a competition golf ball must be at least 1.680 inches in diameter; however, golf balls of any size can be used for leisure golf play. The preferred diameter of the golf balls is from about 1.680 inches to about 1.800 inches. The more preferred diameter is from about 1.680 inches to about 1.760 inches. A diameter of from about 1.680 inches to about 1.740 inches is most preferred; however diameters anywhere in the range of from 1.70 to about 2.0 inches can be used. Oversize golf balls with diameters above about 1.760 inches to as big as 2.75 inches are also within the scope of the invention.

Typical multilayer golf ball constructions feature a polybutadiene core surrounded by one or more thermoplastic intermediate layers and a cover layer. High end tour balls often feature a polybutadiene core surrounded by thermoplastic intermediate layers and a thermoset polyurethane or thermoset polyurea cover layer. Typically the core has a higher specific gravity than the injection molded thermoplastic intermediate layers surrounding it (˜0.98). To conform to U.S.G.A. guidelines and regulations, golf balls also have to be constructed to meet specific weight requirements. When a golf ball is below specified weight requirements, one of the techniques used to increase weight is to add weight-adjusting fillers to the golf ball core formulation. Conventional fillers used include calcium carbonate (specific gravity of 2.73), barium sulfate (sp. gr. of 4.3) and zinc oxide (sp. gr. 5.6). Although these materials can be effectively used to increase the weight of a golf ball, the inevitable volume occupied by these materials when incorporated into a center or core often results in a reduction in the polymer/rubber content of the center or core and hence its resilience. An additional detrimental side effect is that a high loading of fillers stiffens the rubber compound and increases the compression of the core or center while reducing the resilience properties.

Attempts to shift the center of gravity of the golf ball outwards from the center of the ball in order to reduce the spin and increase their distance have involved the development of so called dual cores in which additional regions of polybutadiene are compression molded around the central polybutadiene core with higher levels of density adjusting fillers in the additional polybutadiene region rather than the central one. Alternatively, golf ball cores have been utilized using less dense materials including liquid or foam filled centers to shift the center of gravity outwards but this results in a loss of resilience of the core and concomitant loss of distance on striking the resulting golf ball. Efforts to maintain the high resilience polybutadiene core but increase the specific gravity of the intermediate layers surrounding the core by introducing heavy fillers into the materials used to form the intermediate layers have also been limited by the requirement that the material flow easily in order to be injection molded around the core.

We have now found that it is possible to prepare a golf ball having a low specific gravity core surrounded by one or more intermediate layers which contain sufficient density adjusting fillers to produce a high specific gravity which in turn significantly decreases the spin of the golf ball. In addition, the high specific gravity intermediate layer(s) can be easily injection molded around the low specific gravity core.

The preferred material for the one or more high specific gravity intermediate layers of the golf balls of the present invention are the family of polyalkenamers. The polyalkenamers may be prepared by ring opening metathesis polymerization of one or more cycloalkenes in the presence of organometallic catalysts as described in U.S. Pat. Nos. 3,492,245, and 3,804,803, the entire contents of both of which are herein incorporated by reference. Examples of suitable polyalkenamer rubbers are polypentenamer rubber, polyheptenamer rubber, polyoctenamer rubber, polydecenamer rubber and polydodecenamer rubber. For further details concerning polyalkenamer rubber, see Rubber Chem. & Tech., Vol. 47, page 511-596, 1974, which is incorporated herein by reference.

The polyalkenamer rubbers used in the present invention have a trans-content of from about 40 to about 95, preferably of from about 45 to about 90, and most preferably from about 50 to about 85 wt %, and a cis-content of from about 5 to about 60, preferably of from about 10 to about 55, and most preferably from about 15 to about 50 wt % with a melting point of greater than about 15, preferably greater than about 20 more preferably greater than about 25, more preferably greater than about 30 and most preferably greater than about 45° C. . The polyalkenamers exhibit excellent melt processability above their sharp melting temperatures and high miscibility with various rubber additives as a major component without deterioration of crystallinity which in turn facilitates injection molding. Thus, unlike synthetic rubbers typically used in golf ball preparation, polyalkenamer-based compounds can be prepared which are easily injection moldable. The polyalkenamer rubbers may also be blended with other polymers and an especially preferred blend is that of a polyalkenamer and a polyamide. A more complete description of the polyalkenamer rubbers and blends with polyamides is disclosed in U.S. Pat. Nos. 7,528,196 and 7,874,940 in the name of Hyun Kim et al., the entire contents of each of which are hereby incorporated by reference.

Polyoctenamer rubbers are commercially available from Huls AG of Marl, Germany, and through its distributor in the U.S., Creanova Inc. of Somerset, N.J., and sold under the trademark VESTENAMER®. Two grades of the VESTENAMER® trans-polyoctenamer are commercially available: VESTENAMER 8012 designates a material having a trans-content of approximately 80% (and a cis- content of 20%) with a melting point of approximately 54° C.; and VESTENAMER 6213 designates a material having a trans-content of approximately 60% (cis- content of 40%) with a melting point of approximately 30° C. Both of these polymers have a double bond at every eighth carbon atom in the ring.

When used to form the high specific gravity intermediate layer layers of the golf balls of the present invention, the properties of the polyalkenamer such as compression, hardness and modulus may be further modified by crosslinking using various cross linking packages including crosslinking agents, co-crosslinking agents, peptizers and accelerators.

Suitable cross-linking agents include peroxides, sulfur compounds, or other known chemical cross-linking agents, as well as mixtures of these. Non-limiting examples of suitable cross-linking agents include primary, secondary, or tertiary aliphatic or aromatic organic peroxides. Peroxides containing more than one peroxy group can be used, such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and 1,4-di-(2-tert-butyl peroxyisopropyl)benzene. Both symmetrical and asymmetrical peroxides can be used, for example, tert-butyl perbenzoate and tert-butyl cumyl peroxide. Peroxides incorporating carboxyl groups also are suitable. Non-limiting examples of suitable peroxides include: diacetyl peroxide; di-tert-butyl peroxide; dibenzoyl peroxide; dicumyl peroxide; 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; 1,4-bis-(t-butylperoxyisopropyl)benzene; t-butylperoxybenzoate; 2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3, such as Trigonox 145-45B, marketed by Akrochem Corp. of Akron, Ohio; 1,1-bis(t-butylperoxy)-3,3,5 tri-methylcyclohexane, such as Varox 231-XL, marketed by R.T. Vanderbilt Co., Inc. of Norwalk, Conn.; and di-(2,4-dichlorobenzoyl)peroxide. The cross-linking agents can be blended in total amounts of about 0.05 part to about 5 parts, more preferably about 0.2 part to about 3 parts, and most preferably about 0.2 part to about 2 parts, by weight of the cross-linking agents per 100 parts by weight of the polyalkenamer. Besides the use of chemical cross-linking agents, exposure of the polyalkenamer composition to radiation also can serve as a cross-linking agent. Radiation can be applied to the unsaturated polymer mixture by any known method, including using microwave or gamma radiation, or an electron beam device. Additives may also be used to improve radiation curing of the diene polymer.

The polyalkenamer rubber and cross-linking agent may be blended with a co-cross-linking agent, which may be a metal salt of an unsaturated carboxylic acid. Examples of these include zinc and magnesium salts of unsaturated fatty acids having 3 to 8 carbon atoms, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and palmitic acid, with the zinc salts of acrylic and methacrylic acid, zinc diacrylate and zinc dimethacrylate being most preferred. The unsaturated carboxylic acid metal salt can be blended in a rubber either as a preformed metal salt, or by introducing an α,β-unsaturated carboxylic acid and a metal oxide or hydroxide into the polyalkenamer composition, and allowing them to react in the polyalkenamer composition to form a metal salt. The unsaturated carboxylic acid metal salt can be blended in any desired amount, but preferably in amounts of about 30 parts to about 140 parts by weight of the unsaturated carboxylic acid per 100 parts by weight of the polyalkenamer.

The polyalkenamer compositions used in the present invention may also incorporate one or more of the so-called “peptizers”. The peptizer preferably comprises an organic sulfur compound and/or its metal or non-metal salt. Examples of such organic sulfur compounds include thiophenols, such as pentachlorothiophenol, 4-butyl-o-thiocresol, 4 t-butyl-p-thiocresol, and 2-benzamidothiophenol; thiocarboxylic acids, such as thiobenzoic acid; 4,4′ dithio dimorpholine; and, sulfides, such as dixylyl disulfide, dibenzoyl disulfide; dibenzothiazyl disulfide; di(pentachlorophenyl)disulfide; dibenzamido diphenyldisulfide (DBDD), and alkylated phenol sulfides, such as VULTAC marketed by Atofina Chemicals, Inc. of Philadelphia, Pa. Preferred organic sulfur compounds include pentachlorothiophenol, and dibenzamido diphenyldisulfide.

Examples of the metal salt of an organic sulfur compound include sodium, potassium, lithium, magnesium calcium, barium, and cesium and zinc salts of the above-mentioned thiophenols and thiocarboxylic acids, with the zinc salt of pentachlorothiophenol being most preferred.

Examples of the non-metal salt of an organic sulfur compound include ammonium salts of the above-mentioned thiophenols and thiocarboxylic acids wherein the ammonium cation has the general formula [NR¹R²R³R⁴]⁺ where R¹, R², R³ and R⁴ are selected from the group consisting of hydrogen, a C₁-C₂₀ aliphatic, cycloaliphatic or aromatic moiety, and any and all combinations thereof, with the most preferred being the NH₄ ⁺-salt of pentachlorothiophenol.

Additional peptizers include aromatic or conjugated peptizers comprising one or more heteroatoms, such as nitrogen, oxygen and/or sulfur. More typically, such peptizers are heteroaryl or heterocyclic compounds having at least one heteroatom, and potentially plural heteroatoms, where the plural heteroatoms may be the same or different. Such peptizers include heterocycles such as an indole peptizer, a quinoline peptizer, an isoquinoline peptizer, a pyridine peptizer, purine peptizer, a pyrimidine peptizer, a diazine peptizer, a pyrazine peptizer, a triazine peptizer, a carbazole peptizer, or combinations of such peptizers.

Suitable peptizers also may include one or more additional functional groups, such as halogens, particularly chlorine; a sulfur-containing moiety exemplified by thiols, where the functional group is sulfhydryl (—SH), thioethers, where the functional group is —SR, disulfides, (R₁S—SR₂), etc.; and combinations of functional groups. Such peptizers are more fully disclosed in U.S. Pat. No. 8,030,411 in the name of Hyun Kim et al, the entire contents of which are herein incorporated by reference. A most preferred example is 2, 3, 5, 6-tetrachloro-4-pyridinethiol (TCPT).

The peptizer, if employed in the polyalkenamer composition, is present in an amount up to about 10, from about 0.01 to about 10, preferably of from about 0.10 to about 7, more preferably of from about 0.15 to about 5 parts by weight per 100 parts by weight of the polyalkenamer.

The polyalkenamer compositions used to form the golf balls of the present invention may also include the various fillers as previously described herein. Especially preferred fillers include the one or more so called nanofillers, as described in U.S. Pat. No. 6,794,447 and copending U.S. Publication No. US2004-0092336 filed on Sep. 24, 2003 and U.S. Pat. No. 7,332,533 filed on Aug. 25, 2004, the entire contents of each of which are incorporated herein by reference.

In order to prepare a high specific gravity polyalkenamer-based intermediate layer, additional weight adjusted fillers including density-increasing fillers may be added to the polyalkenamer composition at the level required to attain the desired specific gravity and resilience but also while maintaining sufficient flow properties of the composition such that it remains injection moldable. A feature of the polyalkenamer compositions used to form the intermediate layer of the golf balls of the present invention is that they remain injection moldable (that is they exhibit a relatively low viscosity) even when exhibiting a high specific gravity as a result of the introduction of high concentrations of density-increasing fillers. Conventional density-increasing fillers may be used at very high concentrations including calcium carbonate (specific gravity of 2.73), barium sulfate (sp. gr. of 4.3) and zinc oxide (sp. gr. 5.6). In addition, even higher density fillers having specific gravities of about 6 or greater can be used to increase the specific gravity of the intermediate layer without significantly reducing the flow characteristics of the material and the rebound characteristics of the resulting golf ball. The following Table 1 contains a list of high density inorganic elements and compounds that meet the aforementioned criteria. The list is provided by way of illustration and not limitation.

TABLE 1 Inorganic Element Specific Gravity Tungsten 19.3 Bismuth 9.8 Copper 8.9 Bismuth oxide 8.9 Nickel 8.9 Cobalt 8.9 Iron/Steel 7.7 Tin 7.3 Chromium 7.2 Zinc 7.1 Bismuth carbonate 6.9 Cupric oxide 6.4 Barium tungstate 6.4 Cuprous oxide 6.0 Ferrous oxide 5.7

In one embodiment, the one or more intermediate layers incorporating such fillers are prepared by dry mixing the polyalkenamer rubber with the filler of choice and other crosslinking ingredients to create the desired blend. Mixing can be accomplished in an internal mixer such as a Banbury mixer or an open mill as is well known in the art,

We have now surprisingly found the polyalkenamer compositions comprising the crosslinking packages and fillers are injection moldable such that they exhibit a viscosity using a Dynamic Mechanical Analyzer (DMA) and ASTM D4440 at 200° C. of less than about 5,000 Pa-sec, preferably less than about 3,000 Pa-sec, more preferably less than about 2,000 Pa-sec and even more preferably less than about 1,000 Pa-sec., all at filler levels sufficient to produce a composition with a high specific gravity of greater than or equal to 1.05, preferably greater than or equal to 1.10, more preferably greater than or equal to 1.12, and even more preferably greater than or equal to 1.15.

The polyalkenamer compositions comprising the crosslinking packages and fillers are injection moldable such that they exhibit a storage modulus (G′) measured using a Dynamic Mechanical Analyzer (DMA) and ASTM D4065, at 25° C., and 1 Hz of greater than about 1×10⁷ dyn/cm², preferably greater than about 1.5×10⁷ dyn/cm², more preferably greater than about 1×10⁸ dyn/cm², and most preferably greater than about 2×10⁸ dyn/cm², all at filler levels sufficient to produce a composition with a high specific gravity of greater than or equal to 1.05, preferably greater than or equal to 1.10, more preferably greater than or equal to 1.12, and even more preferably greater than or equal to 1.15.

In certain embodiments, the high specific gravity polyalkenamer composition (that optionally includes fillers) is the majority ingredient of the material used to form at least one intermediate layer of the golf ball. As used herein “majority ingredient” means that the polyalkenamer composition is present in an amount of at least about 75 wt %, particularly at least 90 wt %, and more particularly at least 95 wt %, and most particularly at least 99 wt %, based on the total weight of all the ingredients in the final material used to form at least one intermediate layer.

In order to minimize the spin on the golf ball, the earlier-described high specific gravity intermediate layers are injection molded around a core having a low specific gravity. There are a number of ways to accomplish this, including forming a core from a material with itself has a low specific gravity including the various synthetic foams or alternatively from natural cork.

A variety of thermoplastic polymeric and resinous materials may be expanded to porous, multicellular, solidified foam-like structures by the action of various propellants or agents for expanding or blowing the materials. The unexpanded material may be in the form of a thermoplastic gel and the like or it may be in the form of completely unexpanded or further expandable discrete particles such as granules, beads and similar forms. The blowing agents, in accordance with common practice, are usually gases, gas generating substances or highly fugacious liquids, which may or may not be solvents for the thermoplastic resinous material that have been dissolved or otherwise intimately incorporated within the thermoplastic resinous material while it is in an unexpanded form. The presence or application of heat to an unfoamed thermoplastic material containing a blowing agent causes the blowing agent to be released or thermally expanded, or both, while the thermoplastic material is at or attaining a foaming temperature at which it is sufficiently softened and yieldable to permit the pressure of the thermally expanding blowing agent to expand it into the desired foam structure. In many cases the foaming may be accomplished by simultaneously releasing the blowing agent-containing material from a confining pressure while it is at or being heated to a foaming temperature.

Foamed cores for use in the golf balls of the present invention may be formed from any number of specific materials commonly used to prepare foams such as polyurethane, polyurea , polyethylene, polystyrene, polyisoprene, ethylene vinyl acetate (EVA), ethylene propylene diene monomer (EPDM), polyester, polypropylene, polybutadiene, polyisoprene, ionomer, nylon, acetal, teflon, polycarbonate, acrylic, neoprene, silicone, polymethylpentene, acrylonitrile butadiene styrene (ABS), polyetheretherketone, polyvinyl chloride, chlorinated polyethylene (CPE) polyisocyanurate acrylate copolymers, such as EMA, EBA, NUCREL® type acid co and terpolymers, ethylene propylene rubber (such as EPR, EPDM, and any ethylene copolymers), styrene-butadiene, SEBS (any Kraton-type), PVC, PVDC, polyalkenamer, epoxy foams, urea-formaldehyde foams, latex foams and sponge, silicone foams, flouorpolymer foams and syntactic foams (hollow sphere filled) or the like.

Polymer foam structures may be prepared by blending and heating a polymer material and a decomposable chemical blowing agent to form a foamable plasticized or melt polymer material, extruding the foamable melt polymer material through a die, optionally inducing cross-linking in the melt polymer material, and exposing the melt polymer material to an elevated temperature to release the blowing agent to form the foam structure. The polymer material and the chemical blowing agent may be mixed and melt blended by any means known in the art such as with an extruder, mixer, blender, or the like. The chemical blowing agent is preferably dry-blended with the polymer material prior to heating the polymer material to a melt form, but may also be added when the polymer material is in melt phase. Cross-linking may be induced by addition of a cross-linking agent or by radiation. If required induction of cross-linking and exposure to an elevated temperature to effect foaming or expansion may occur simultaneously or sequentially. If a cross-linking agent is used, it is incorporated into the polymer material in the same manner as the chemical blowing agent. Further, if a cross-linking agent is used, the foamable melt polymer material is heated or exposed to a temperature of preferably less than the decomposition temperature of the cross-linking agent or the blowing agent and to prevent premature cross-linking. The foamable melt polymer material may then be extruded or conveyed through a die of desired shape to form the golf ball cores used in the present invention.

Foam structures may also be formed into cross-linked foam beads suitable for molding into articles. To make the foam beads, discrete resin particles such as granulated resin pellets are: suspended in a liquid medium in which they are substantially insoluble such as water; impregnated with a cross-linking agent and a blowing agent at an elevated pressure and temperature in an autoclave or other pressure vessel; and rapidly discharged into the atmosphere or a region of reduced pressure to expand to form the foam beads. The foam beads may then be molded by any means known in the art to form the golf ball cores of the present invention.

Alternatively, the foam beads can also be prepared by preparing a mixture of polymer, cross-linking agent, and decomposable mixtures in a suitable mixing device or extruder and form the mixture into pellets, and heat the pellets to cross-link and expand.

Finally cross-linked foam beads suitable for molding into the golf ball cores of the present invention may also be prepared by melting and mixing the polymer material with a physical blowing agent in a conventional foam extrusion apparatus to form an essentially continuous foam strand. The foam strand may then be granulated or pelletized to form foam beads. If desired, the foam beads may then be cross-linked by radiation. The cross-linked foam beads may then be coalesced and molded to form the golf ball cores of the present invention.

A special class of closed-cell foams are foams containing microspheres embedded in a matrix material. The low specific gravity core can be made from a thermosetting foam with hollow sphere fillers or microspheres in a polymeric matrix of epoxy, urethane, polyester or any suitable thermosetting binder. Additional materials include the closed-cell foams incorporating microspheres as described in U.S. Pat. No. 7,073,277, which is incorporated by reference herein in its entirety. Other exemplary materials that may be used in the golf ball of the present invention are described in U.S. Pat. No. 5,824,746, U.S. Pat. No. 6,025,442 and U.S. Pat. No. 7,708,654, all of which are incorporated by reference herein in their entireties.

The gas phase in the foamed core component is distributed in voids, pores, or pockets referred to herein as cells. If these cells are interconnected in such a manner that gas can pass from one to another, the material is termed open-celled. If the cells are discrete and the gas phase of each is independent of that of the other cells, the material is termed closed-celled.

The blowing agents suitable for use to prepare the foamed cores of the golf balls of the present invention include CO₂ or N₂ or the chemical blowing agents, for example, isobutane, isopentane, azo compounds, or any chemical blowing agent which releases upon exposure to thermal or radiational energy. Other blowing agents useful in making the present foams include inorganic blowing agents, organic blowing agents and chemical blowing agents. Suitable inorganic blowing agents include sulfur hexafluoride (SF₆), argon, water, air and helium. Organic blowing agents include carbon dioxide, aliphatic hydrocarbons having 1-9 carbon atoms, aliphatic alcohols having 1-3 carbon atoms, and fully and partially halogenated aliphatic hydrocarbons having 1-4 carbon atoms. Aliphatic hydrocarbons include methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, neopentane, and the like. Aliphatic alcohols include methanol, ethanol, n-propanol, and isopropanol. Fully and partially halogenated aliphatic hydrocarbons include fluorocarbons, chlorocarbons, and chlorofluorocarbons. Examples of fluorocarbons include methyl fluoride, perfluoromethane, ethyl fluoride,), 1,1-difluoroethane (HFC-152a), fluoroethane (HFC-161), 1,1,1-trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,2,2 tetrafluoroethane (HFC-134), 1, 1,1,3,3-pentafluoropropane, pentafluoroethane (HFC-125), difluoromethane (HFC-32), perfluoroethane, 2,2-difluoropropane, 1,1,1-trifluoropropane, perfluoropropane, dichloropropane, difluoropropane, perfluorobutane, perfluorocyclobutane. Partially halogenated chlorocarbons and chlorofluorocarbons for use in this invention include methyl chloride, methylene chloride, ethyl chloride, 1,1,1-trichloro-ethane, 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b), chlorodifluoromethane (HCFC-22), 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) and 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124). Fully halogenated chlorofluorocarbons include trichloromonofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), trichloro-trifluoroethane (CFC-113), dichlorotetrafluoroethane (CFC-114), chloroheptafluoropropane, and dichlorohexafluoropropane. Chemical blowing agents include azodicarbonamide, azodiisobutyro-nitrile, benzenesulfonhydrazide, 4,4-oxybenzene sulfonyl-semicarbazide, p-toluene sulfonyl semi-carbazide, barium azodicarboxylate, N,N′-dimethyl-N,N′-dinitroso-terephthalanide, trihydrazino triazine and mixtures of citric acid and sodium bicarbonate such as the various products sold under the name Hydrocerol®. (a product and trademark of Boehringer Ingelheim). Suitable blowing agents may also include, but are not limited to, azodicarbonamide, N,N-dinitroso-pentamethylene-tetetramine, 4-4 oxybis (benzenesulfonyl-hydrazide), and sodium bicarbonate. All of these blowing agents may be used as single components or any mixture of combination thereof, or in mixtures with other co-blowing agents.

One material especially suitable to prepare the foamed cores for use in the present invention are foams made from polyethylene. Excellent teachings to processes for making ethylenic polymer foam structures and processing them can be found in C. P. Park, “Polyolefin Foam”, Chapter 9, Handbook of Polymer Foams and Technology, edited by D. Klempner and K. C. Frisch, Hanser Publishers, Munich, Vienna, N.Y., Barcelona (1991), pp. 224-233, as well as U.S. Pat. No. 3,616,365, U.S. Pat. No. 3,886, 100, U.S. Pat. No. 3,959,189, U.S. Pat. No. 4,168,353, and U.S. Pat. No. 4,429,059, the teachings of each which are incorporated herein by reference.

A preferred material to form the foamed golf ball cores for use in the present invention includes an alkenyl aromatic polymer such as polystyrene. The most preferable types of styrenic foams employed are the closed-cell extruded foams and expanded bead foams. Generally, polystyrene foams for the present application preferably have a relatively small cell size which exhibits excellent dimensional stability. Extruded polystyrene foams oftentimes exhibit substantial benefits such as high compression, tensile strength and the like. In extruded foams, depending upon the conditions of extrusion, maximum compressive strength may be obtained either in the direction of extrusion or in a direction transverse to the direction of extrusion

Another preferred material for use in the foamed golf ball cores of the present invention are foams prepared from blends of polystyrene and polyethylene resins. Japanese Patent Publication No. 34,662/1977 discloses a method of mixing the two resins in the presence of a specific mixed medium and Japanese Patent Laying-Open No. 35,471/1974 describes a method of polymerizing styrene as contained in polyethylene resin; both of these methods being ultimately directed toward foaming the combined resins. U.S. Pat. No. 4,652,588 (the disclosure of which is herein incorporated by reference in its entirety) discloses extruded or bead foams prepared from a blend of an ethylenic polymer resin with a melt index (MI) in the range of from 0.2 to 2.6 g/10 minutes and a styrenic polymer resin with a melt flow index (MFI) in the range of from 1.4 to 18 g/10 minutes, to yield a foam which exhibits a well-balanced combination of flexibility and compression strength, excellence in compression recovery, resistance to distortion due to repeating compression, and high durability.

Another material especially suitable to prepare the foamed cores for use in the present invention are foams made from an ionomer modified polyolefin foam which is essentially closed cell in structure. The polyolefin used is preferably a low density polyethylene or a polypropylene resin which during extrusion with proper additives will form a fine, closed cell foam. The ionomer resins employed in the basic foamable mixture are derived from ethylene/(meth)acrylic acid copolymers and include the family of “Surlyn” ionomers (a registered trademark of DuPont Co.).

Another material especially suitable to prepare the foamed cores for use in the present invention is polyurethane. Generally, polyurethane and polyurea foams are prepared by reacting an organic polyisocyanate with an active hydrogen-containing compound in the presence of the blowing agent or agents. The preparation of polyurethane foam has been described for example, in U.S. Pat. No. 4,076,644: U.S. Pat. No. 4,264,970: and U.S. Pat. No. 4,636,529 the disclosures of each of which are herein incorporated by reference. Alternatively, polyurethane and polyurea foams may be prepared by reaction injection molding, where a gas, typically nitrogen, is essentially whipped into at least one component of the polyurethane, typically, the pre-polymer, prior to component injection into a closed mold where full reaction takes place resulting in a cured polymer having a reduced specific gravity.

In addition to foams, materials with a sufficiently low specific gravity are also suitable for core preparation without the requirement that they be foamed. The specific gravity of this material may also be less than 0.9 and preferably less than 0.8, and includes materials such as selected metallocene-catalyzed polymers, ionomers, or other polyolefinic materials. Other suitable materials include polyurethanes, polyurethane ionomers, interpenetrating polymer networks, HYTREL® (polyester-ether elastomer) or PEBAX® (polyamide-ester elastomer), etc., which may have specific gravity of less than 1.0. Additionally, suitable unmodified materials are also disclosed in U.S. Pat. No. 6,419, 535, U.S. Pat. No. 6,152,834, U.S. Pat. No. 5,919,100, U.S. Pat. No. 5,885,172 and WO 00/57962. These references are incorporated herein by reference.

Finally, in one embodiment of the present invention, the low specific gravity core may be formed from natural cork which is a natural impermeable and lightweight material derived from the bark of cork oak trees, most of which are found in countries bordering the Mediterranean, in Europe and in North Africa. Although cork is used particularly for making bottle corks used to close wine bottles, it also has properties particularly well suited for the golf ball cores used in the present invention including its elasticity, resiliency, and compressibility. One embodiment of the golf ball of the present invention may use a natural cork such as a pressed cork having a coefficient of restitution of from about 0.3 to about 0.8, a compressive strength of from about 50 psi to about 250 psi , a ductility of from about 5 to about 25% elongation at break, a shear modulus of from about 200 to about 1000 psi , a tensile yield strength of from about 50 to about 150 psi, an ultimate tensile strength of from about 50 to about 200 psi and a Young's Modulus of from about 1,500 to about 3,500 psi.

In addition to the cork or foamed cellular core and high specific gravity polyalkenamer intermediate layer(s), other materials may also be used as a separate component of the core, cover layer or intermediate layers of the golf balls of the present invention. These other materials include, without limitation, synthetic and natural rubbers, thermoset polymers such as thermoset polyurethanes or thermoset polyureas, as well as thermoplastic polymers including thermoplastic elastomers such as metallocene catalyzed polymer, unimodal ethylene/carboxylic acid copolymers, unimodal ethylene/carboxylic acid/carboxylate terpolymers, bimodal ethylene/carboxylic acid copolymers, bimodal ethylene/carboxylic acid/carboxylate terpolymers, thermoplastic polyurethanes, thermoplastic polyureas, polyamides, copolyamides, polyesters, copolyesters, polycarbonates, polyolefins, halogenated (e.g. chlorinated) polyolefins, halogenated polyalkylene compounds, such as halogenated polyethylene [e.g. chlorinated polyethylene (CPE)], polyalkenamer, polyphenylene oxides, polyphenylene sulfides, diallyl phthalate polymers, polyimides, polyvinyl chlorides, polyamide-ionomers, polyurethane-ionomers, polyvinyl alcohols, polyarylates, polyacrylates, polyphenylene ethers, impact-modified polyphenylene ethers, polystyrenes, high impact polystyrenes, acrylonitrile-butadiene-styrene copolymers, styrene-acrylonitriles (SAN), acrylonitrile-styrene-acrylonitriles, styrene-maleic anhydride (S/MA) polymers, styrenic block copolymers including styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene, (SEBS) and styrene-ethylene-propylene-styrene (SEPS), styrenic terpolymers , functionalized styrenic block copolymers including hydroxylated, functionalized styrenic copolymers, and terpolymers, cellulosic polymers, liquid crystal polymers (LCP), ethylene-propylene-diene terpolymers (EPDM), ethylene-vinyl acetate copolymers (EVA), ethylene-propylene copolymers, propylene elastomers (such as those described in U.S. Pat. No. 6,525,157, to Kim et al, the entire contents of which is hereby incorporated by reference), ethylene vinyl acetates, polyureas, and polysiloxanes and any and all combinations thereof.

One preferred material which may be used as a separate component of the cover layer or intermediate layer of the golf balls of the present invention is a block copolymer including di and triblock copolymers incorporating a first polymer block having an aromatic vinyl compound, and a second polymer block having an olefinic and/or conjugated diene compound. Preferred aromatic vinyl compounds include styrene, α-methylstyrene, o-, m- or p-methylstyrene, 4-propylstyrene, 1,3-dimethylstyrene, vinylnaphthalene and vinylanthracene. In particular, styrene and α-methylstyrene are preferred. These aromatic vinyl compounds can each be used alone, or can be used in combination of two or more kinds. The aromatic vinyl compound is preferably contained in the block copolymer in an amount of from 5 to 75% by weight, and more preferably from 10 to 65% by weight.

The conjugated diene compound, that constitutes another polymer block in the block copolymer can include for example, 1,3-butadiene, isoprene, 2,3-diemthyl-1,3-butadiene, 1,3-pentadiene and 1,3-hexadiene. In particular, isoprene and 1,3-butadiene are preferred. These conjugated diene compounds can each be used alone, or can be used in combination of two or more kinds.

Preferred block copolymers include the styrenic block copolymers such as styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene, (SEBS) and styrene-ethylene-propylene-styrene (SEPS). Commercial examples include SEPTON® marketed by Kuraray Company of Kurashiki, Japan; TOPRENE by Kumho Petrochemical Co., Ltd and KRATON® marketed by Kraton Polymers. Also included are functionalized styrenic block copolymers, including those where the block copolymer incorporates a first polymer block having an aromatic vinyl compound, a second polymer block having a conjugated diene compound and a hydroxyl group located at a block copolymer, or its hydrogenation product. One such functionalized styrenic block copolymer is SEPTON HG-252.

Another preferred material which may be used as a separate component of the cover layer or intermediate layer of the golf balls of the present invention is an acidic polymer that incorporates at least one type of an acidic functional group. Examples of such acidic polymers suitable for use as include, but are not limited to, ethylene/(meth)acrylic acid copolymers and ethylene/(meth)acrylic acid/ alkyl(meth)acrylate terpolymers, or ethylene and/or propylene maleic anhydride copolymers and terpolymers. Examples of such polymers which are commercially available include, but are not limited to, the ESCOR® 5000, 5001, 5020, 5050, 5070, 5100, 5110 and 5200 series of ethylene-acrylic acid copolymers sold by Exxon Mobil, the PRIMACOR® 1321, 1410, 1410-XT, 1420, 1430, 2912, 3150, 3330, 3340, 3440, 3460, 4311, 4608 and 5980 series of ethylene-acrylic acid copolymers sold by The Dow Chemical Company, Midland, Michigan and the ethylene-methacrylic acid copolymers such as NUCREL® 599, 699, 0903, 0910, 925, 960, 2806, and 2906 sold by DuPont

Also included are the so called bimodal ethylene/carboxylic acid polymers as described in U.S. Pat. No. 6,562,906, the contents of which are incorporated herein by reference. These polymers comprise a first component comprising an ethylene/α, β-ethylenically unsaturated C₃₋₈ carboxylic acid high copolymer, particularly ethylene(meth)acrylic acid copolymers and ethylene, alkyl(meth)acrylate, (meth)acrylic acid terpolymers, having a weight average molecular weight, Mw, of about 80,000 to about 500,000, and a second component comprising an ethylene/α, β-ethylenically unsaturated C₃₋₈ carboxylic acid copolymers, particularly ethylene/(meth)acrylic acid copolymers having weight average molecular weight, Mw, of about 2,000 to about 30,000.

Another preferred material which may be used as a separate component of the cover layer or intermediate layer of the golf balls of the present invention is an ionomer resin. One family of such resins was developed in the mid-1960's, by E.I. DuPont de Nemours and Co., and is sold under the trademark SURLYN®. Preparation of such ionomers is well known, for example see U.S. Pat. No. 3,264,272. Generally speaking, most commercial ionomers are unimodal and consist of a polymer of a mono-olefin, e.g., an alkene, with an unsaturated mono- or dicarboxylic acids having 3 to 12 carbon atoms. An additional monomer in the form of a mono- or dicarboxylic acid ester may also be incorporated in the formulation as a so-called “softening comonomer”. The incorporated carboxylic acid groups are then neutralized by a basic metal ion salt, to form the ionomer. The metal cations of the basic metal ion salt used for neutralization include Li⁺, Na⁺, K⁺, Zn²⁺, Ca²⁺, Co²⁺, Ni²⁺, Cu²⁺, Pb²⁺, and Mg²⁺, with the Li⁺, Na⁺, Ca²⁺, Zn²⁺, and Mg²⁺ being preferred. The basic metal ion salts include those of for example formic acid, acetic acid, nitric acid, and carbonic acid, hydrogen carbonate salts, oxides, hydroxides, and alkoxides.

The first commercially available ionomer resins contained up to 16 weight percent acrylic or methacrylic acid, although it was also well known at that time that, as a general rule, the hardness of these cover materials could be increased with increasing acid content. Hence, in Research Disclosure 29703, published in January 1989, DuPont disclosed ionomers based on ethylene/acrylic acid or ethylene/methacrylic acid containing acid contents of greater than 15 weight percent. In this same disclosure, DuPont also taught that such so called “high acid ionomers” had significantly improved stiffness and hardness and thus could be advantageously used in golf ball construction, when used either singly or in a blend with other ionomers.

More recently, high acid ionomers can be ionomer resins with acrylic or methacrylic acid units present from 16 wt. % to about 35 wt. % in the polymer. Generally, such a high acid ionomer will have a flexural modulus from about 50,000 psi to about 125,000 psi.

Ionomer resins further comprising a softening comonomer, present from about 10 wt. % to about 50 wt. % in the polymer, have a flexural modulus from about 2,000 psi to about 10,000 psi, and are sometimes referred to as “soft” or “very low modulus” ionomers. Typical softening comonomers include n-butyl acrylate, iso-butyl acrylate, n-butyl methacrylate, methyl acrylate and methyl methacrylate.

Today, there are a wide variety of commercially available ionomer resins based both on copolymers of ethylene and (meth)acrylic acid or terpolymers of ethylene and (meth)acrylic acid and (meth)acrylate, many of which are be used as a golf ball component. The properties of these ionomer resins can vary widely due to variations in acid content, softening comonomer content, the degree of neutralization, and the type of metal ion used in the neutralization. The full range commercially available typically includes ionomers of polymers of general formula, E/X/Y polymer, wherein E is ethylene, X is a C₃ to C₈ α,β ethylenically unsaturated carboxylic acid, such as acrylic or methacrylic acid, and is present in an amount from about 2 to about 30 weight % of the E/X/Y copolymer, and Y is a softening comonomer selected from the group consisting of alkyl acrylate and alkyl methacrylate, such as methyl acrylate or methyl methacrylate, and wherein the alkyl groups have from 1-8 carbon atoms, Y is in the range of 0 to about 50 weight % of the E/X/Y copolymer, and wherein the acid groups present in said ionomeric polymer are partially neutralized with a basic metal salt with metal ions selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc or aluminum, or a combination of such cations.

The ionomer may also be a so-called bimodal ionomer as described in U.S. Pat. No. 6,562,906 (the entire contents of which are herein incorporated by reference). These ionomers are bimodal as they are prepared from blends comprising polymers of different molecular weights. Specifically they include bimodal polymer blend compositions comprising:

a) a high molecular weight component having a weight average molecular weight, Mw, of about 80,000 to about 500,000 and comprising one or more ethylene/α, β-ethylenically unsaturated C₃₋₈ carboxylic acid copolymers and/or one or more ethylene, alkyl(meth)acrylate, (meth)acrylic acid terpolymers; said high molecular weight component being partially neutralized with a basic metal salt with metal ions selected from the group consisting of lithium, sodium, zinc, calcium, magnesium, and a mixture of any these; and

b) a low molecular weight component having a weight average molecular weight, Mw, of about from about 2,000 to about 30,000 and comprising one or more ethylene/α, β-ethylenically unsaturated C₃₋₈ carboxylic acid copolymers and/or one or more ethylene, alkyl(meth)acrylate, (meth)acrylic acid terpolymers; said low molecular weight component being partially neutralized with a basic metal salt with metal ions selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc or aluminum, and a mixture of any these.

In addition to the unimodal and bimodal ionomers, also included are the so-called “modified ionomers” examples of which are described in U.S. Pat. Nos. 6,100,321, 6,329,458 and 6,616,552 and U.S. Patent Publication US 2003/0158312 A1, the entire contents of all of which are herein incorporated by reference.

The modified unimodal ionomers may be prepared by mixing:

a) an ionomeric polymer comprising ethylene, from 5 to 25 weight percent (meth)acrylic acid, and from 0 to 40 weight percent of a (meth)acrylate monomer, said ionomeric polymer neutralized with a basic metal salt with metal ions selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc or aluminum, and any and all mixtures thereof; and

b) from about 5 to about 40 weight percent (based on the total weight of said modified ionomeric polymer) of one or more fatty acids or metal salts of said fatty acid, the metal salt having metal ions selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc or aluminum, and any and all mixtures thereof; and the fatty acid preferably being stearic acid.

The modified bimodal ionomers, which are ionomers derived from the earlier described bimodal ethylene/carboxylic acid polymers (as described in U.S. Pat. No. 6,562,906, the entire contents of which are herein incorporated by reference), are prepared by mixing;

a) a high molecular weight component having a weight average molecular weight, Mw, of about 80,000 to about 500,000 and comprising one or more ethylene/α, β-ethylenically unsaturated C₃₋₈ carboxylic acid copolymers and/or one or more ethylene, alkyl(meth)acrylate, (meth)acrylic acid terpolymers; said high molecular weight component being partially neutralized with a basic metal salt with metal ions selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc or aluminum, and any and all mixtures thereof; and

b) a low molecular weight component having a weight average molecular weight, Mw, of about from about 2,000 to about 30,000 and comprising one or more ethylene/α, β-ethylenically unsaturated C₃₋₈ carboxylic acid copolymers and/or one or more ethylene, alkyl(meth)acrylate, (meth)acrylic acid terpolymers; said low molecular weight component being partially neutralized with a basic metal salt with metal ions selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc or aluminum, and any and all mixtures thereof; and

c) from about 5 to about 40 weight percent (based on the total weight of said modified ionomeric polymer) of one or more fatty acids or metal salts of said fatty acid, the metal salt having metal ions selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc or aluminum, and any and all mixtures thereof; and the fatty acid preferably being stearic acid.

The fatty or waxy acid salts utilized in the various modified ionomers are composed of a chain of alkyl groups containing from about 4 to 75 carbon atoms (usually even numbered) and characterized by a —COOH terminal group. The fatty or waxy acids utilized to produce the fatty or waxy acid salts modifiers may be saturated or unsaturated, and they may be present in solid, semi-solid or liquid form.

Examples of suitable saturated fatty acids, i.e., fatty acids in which the carbon atoms of the alkyl chain are connected by single bonds, include but are not limited to stearic acid (CH₃(CH₂)₁₆ COOH), palmitic acid (CH₃ (CH₂)₁₄ COOH), pelargonic acid (CH₃ (CH₂)₇ COOH) and lauric acid (CH₃ (CH₂)₁₀ COOH). Examples of suitable unsaturated fatty acids, i.e., a fatty acid in which there are one or more double bonds between the carbon atoms in the alkyl chain, include but are not limited to oleic acid (CH₃ (CH₂)₇ CH:CH(CH₂)₇ COOH).

The source of the metal ions used to produce the metal salts of the fatty or waxy acid salts used in the various modified ionomers are generally various metal salts which provide the metal ions capable of neutralizing, to various extents, the carboxylic acid groups of the fatty acids. These include the sulfate, carbonate, acetate and hydroxylate salts of zinc, barium, calcium and magnesium.

Since the fatty acid salts modifiers comprise various combinations of fatty acids neutralized with a large number of different metal ions, several different types of fatty acid salts may be utilized in the invention, including metal stearates, laureates, oleates, and palmitates, with calcium, zinc, sodium, lithium, potassium and magnesium stearate being preferred, and calcium and sodium stearate being most preferred.

The fatty or waxy acid or metal salt of said fatty or waxy acid is present in the modified ionomeric polymers in an amount of from about 5 to about 40, preferably from about 7 to about 35, more preferably from about 8 to about 20 weight percent (based on the total weight of said modified ionomeric polymer).

As a result of the addition of the one or more metal salts of a fatty or waxy acid, from about 40 to 100, preferably from about 50 to 100, more preferably from about 70 to 100 percent of the acidic groups in the final modified ionomeric polymer composition are neutralized by a metal ion.

An example of such a modified ionomer polymer is DUPONT® HPF-1000 available from E. I. DuPont de Nemours and Co. Inc.

Another preferred material which may be used as a separate component of the cover layer or intermediate layer of the golf balls of the present invention is a multi-component blend composition (“MCBC”) prepared by blending together at least three materials, identified as Components A, B, and C, and melt-processing these components to form in-situ, a polymer blend composition incorporating a pseudo-crosslinked polymer network. Such blends are more fully described in U.S. Pat. No. 6,930,150 to H. J. Kim, the entire contents of which are hereby incorporated by reference.

The first of these blend components (blend Component A) include block copolymers including di and triblock copolymers, incorporating a first polymer block having an aromatic vinyl compound, and a second polymer block having an olefinic and/or conjugated diene compound. Preferred aromatic vinyl compounds include styrene, α-methylstyrene, o-, m- or p-methylstyrene, 4-propylstyrene, 1,3-dimethylstyrene, vinylnaphthalene and vinylanthracene. In particular, styrene and α-methylstyrene are preferred. These aromatic vinyl compounds can each be used alone, or can be used in combination of two or more kinds. The aromatic vinyl compound is preferably contained in the block copolymer (b) in an amount of from 5 to 75% by weight, and more preferably from 10 to 65% by weight.

The conjugated diene compound, that constitutes the polymer block B in the block copolymer (b), includes, e.g., 1,3-butadiene, isoprene, 2, 3-dimethyl-1,3-butadiene, 1,3-pentadiene and 1,3-hexadiene. In particular, isoprene and 1,3-butadiene are preferred. These conjugated diene compounds can each be used alone, or can be used in combination of two or more kinds.

Preferred block copolymers include the styrenic block copolymers such as styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene, (SEBS) and styrene-ethylene-propylene-styrene (SEAS). Commercial examples include SEPTON® marketed by Kuraray Company of Kurashiki, Japan; TOPRENE® by Kumho Petrochemical Co., Ltd and KRATON® marketed by Kraton Polymers.

Also included are functionalized styrenic block copolymers, including those where the block copolymer incorporates a first polymer block having an aromatic vinyl compound, a second polymer block having a conjugated diene compound and a hydroxyl group located at a block copolymer, or its hydrogenation product. A preferred functionalized styrenic block copolymer is SEPTON HG-252.

The second blend component, Component B, is an acidic polymer that incorporates at least one type of an acidic functional group. Examples of such polymers suitable for use as include, but are not limited to, ethylene/(meth)acrylic acid copolymers and ethylene/(meth)acrylic acid/ alkyl(meth)acrylate terpolymers, or ethylene and/or propylene maleic anhydride copolymers and terpolymers. Examples of such polymers which are commercially available include, but are not limited to, the ESCOR® 5000, 5001, 5020, 5050, 5070, 5100, 5110 and 5200 series of ethylene-acrylic acid copolymers sold by Exxon Mobil, the PRIMACOR® 1321, 1410, 1410-XT, 1420, 1430, 2912, 3150, 3330, 3340, 3440, 3460, 4311, 4608 and 5980 series of ethylene-acrylic acid copolymers sold by The Dow Chemical Company, Midland, Mich. and the ethylene-methacrylic acid copolymers such as Nucrel 599, 699, 0903, 0910, 925, 960, 2806, and 2906 commercially available from DuPont. Also included are the so called bimodal ethylene/carboxylic acid polymers as described in U.S. Pat. No. 6,562,906, the contents of which are incorporated herein by reference. These polymers comprise a first component comprising an ethylene/α, β-ethylenically unsaturated C₃₋₈ carboxylic acid high copolymer, particularly ethylene(meth)acrylic acid copolymers and ethylene, alkyl(meth)acrylate, (meth)acrylic acid terpolymers, having a weight average molecular weight, Mw, of about 80,000 to about 500,000, and a second component comprising an ethylene/α, β-ethylenically unsaturated C₃₋₈ carboxylic acid copolymers, particularly ethylene/(meth)acrylic acid copolymers having weight average molecular weight, Mw, of about 2,000 to about 30,000.

Component C is a base capable of neutralizing the acidic functional group of Component B and typically is a base having a metal cation. These metals are from groups IA, IB, IIA, IIB, IIIA, IIIB, IVA, IVB, VA, VB, VIA, VIB, VIIB and VIIIB of the periodic table. Examples of these metals include lithium, sodium, magnesium, aluminum, potassium, calcium, manganese, tungsten, titanium, iron, cobalt, nickel, hafnium, copper, zinc, barium, zirconium, and tin. Suitable metal compounds for use as a source of Component C are, for example, metal salts, preferably metal hydroxides, metal oxides, metal carbonates, metal acetates, metal stearates, metal laureates, metal oleates, metal palmitates and the like.

The MCBC composition preferably is prepared by mixing the above materials into each other thoroughly, either by using a dispersive mixing mechanism, a distributive mixing mechanism, or a combination of these. These mixing methods are well known in the manufacture of polymer blends. As a result of this mixing, the acidic functional group of Component B is dispersed evenly throughout the mixture in either their neutralized or non-neutralized state. Most preferably, Components A and B are melt-mixed together without Component C, with or without the premixing discussed above, to produce a melt-mixture of the two components. Then, Component C separately is mixed into the blend of Components A and B. This mixture is melt-mixed to produce the reaction product. This two-step mixing can be performed in a single process, such as, for example, an extrusion process using a proper barrel length or screw configuration, along with a multiple feeding system.

Another preferred material which may be used as a separate component of the cover layer or intermediate layer of the golf balls of the present invention is a homopolyamide or copolyamide. Illustrative polyamides for use include those obtained by: (1) polycondensation of (a) a dicarboxylic acid, such as oxalic acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, or 1,4-cyclohexanedicarboxylic acid, with (b) a diamine, such as ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, decamethylenediamine, 1,4-cyclohexyldiamine or m-xylylenediamine; (2) a ring-opening polymerization of cyclic lactam, such as c-caprolactam or ω-laurolactam; (3) polycondensation of an aminocarboxylic acid, such as 6-aminocaproic acid, 9-aminononanoic acid, 11-aminoundecanoic acid or 12-aminododecanoic acid; (4) copolymerization of a cyclic lactam with a dicarboxylic acid and a diamine; or any combination of (1)-(4). In certain examples, the dicarboxylic acid may be an aromatic dicarboxylic acid or a cycloaliphatic dicarboxylic acid. In certain examples, the diamine may be an aromatic diamine or a cycloaliphatic diamine. Specific examples of suitable polyamides include polyamide 6; polyamide 11; polyamide 12; polyamide 4,6; polyamide 6,6; polyamide 6,9; polyamide 6,10; polyamide 6,12; polyamide MXD6; PAl2,CX; PAl2, IT; PPA; PA6, IT; and PA6/PPE.

Another preferred material which may be used as a separate component of the cover layer or intermediate layer of the golf balls of the present invention is the family of polyurethanes or polyureas which are typically prepared by reacting a diisocyanate with a polyol (in the case of polyurethanes) or with a polyamine (in the case of a polyurea). Thermoplastic polyurethanes or polyureas may consist solely of this initial mixture or may be further combined with a chain extender to vary properties such as hardness of the thermoplastic. Thermoset polyurethanes or polyureas typically are formed by the reaction of a diisocyanate and a polyol or polyamine respectively, and an additional crosslinking agent to crosslink or cure the material to result in a thermoset.

In what is known as a one-shot process, the three reactants, diisocyanate, polyol or polyamine, and optionally a chain extender or a curing agent, are combined in one step. Alternatively, a two-step process may occur in which the first step involves reacting the diisocyanate and the polyol (in the case of polyurethane) or the polyamine (in the case of a polyurea) to form a so-called prepolymer, to which can then be added either the chain extender or the curing agent. This procedure is known as the prepolymer process.

In addition, although depicted as discrete component packages as above, it is also possible to control the degree of crosslinking, and hence the degree of thermoplastic or thermoset properties in a final composition, by varying the stoichiometry not only of the diisocyanate-to-chain extender or curing agent ratio, but also the initial diisocyanate-to-polyol or polyamine ratio. Of course in the prepolymer process, the initial diisocyanate-to-polyol or polyamine ratio is fixed on selection of the required prepolymer, although mixtures of prepolymers are also contemplated.

Any isocyanate available to one of ordinary skill in the art is suitable for use according to the invention. Isocyanates for use with the present invention include, but are not limited to, aliphatic, cycloaliphatic, aromatic aliphatic, aromatic, any derivatives thereof, and combinations of these compounds having two or more isocyanate (NCO) groups per molecule. As used herein, aromatic aliphatic compounds should be understood as those containing an aromatic ring, wherein the isocyanate group is not directly bonded to the ring. One example of an aromatic aliphatic compound is a tetramethylxylene diisocyanate (TMXDI). The isocyanates may be organic polyisocyanate-terminated prepolymers, low free isocyanate prepolymer, and mixtures thereof The isocyanate-containing reactable component also may include any isocyanate-functional monomer, dimer, trimer, or polymeric adduct thereof, prepolymer, quasi-prepolymer, or mixtures thereof. Isocyanate-functional compounds may include monoisocyanates or polyisocyanates that include any isocyanate functionality of two or more.

Suitable isocyanate-containing components include diisocyanates having the generic structure: O═C═N—R—N═C═O, where R preferably is a cyclic, aromatic, or linear or branched hydrocarbon moiety containing from about 1 to about 50 carbon atoms. The isocyanate also may contain one or more cyclic groups or one or more phenyl groups. When multiple cyclic or aromatic groups are present, linear and/or branched hydrocarbons containing from about 1 to about 10 carbon atoms can be present as spacers between the cyclic or aromatic groups. In some cases, the cyclic or aromatic group(s) may be substituted at the 2-, 3-, and/or 4-positions, or at the ortho-, meta-, and/or para-positions, respectively. Substituted groups may include, but are not limited to, halogens, primary, secondary, or tertiary hydrocarbon groups, or a mixture thereof.

Examples of isocyanates that can be used with the present invention include, but are not limited to, substituted and isomeric mixtures including 2,2′-, 2,4′-, and 4,4′-diphenylmethane diisocyanate (MDI); 3,3′-dimethyl-4,4′-biphenylene diisocyanate (TODI); toluene diisocyanate (TDI); polymeric MDI; carbodiimide-modified liquid 4,4′-diphenylmethane diisocyanate; para-phenylene diisocyanate (PPDI); meta-phenylene diisocyanate (MPDI); triphenyl methane-4,4′- and triphenyl methane-4,4″-triisocyanante; naphthylene-1,5-diisocyanate; 2,4′-, 4,4′-, and 2,2-biphenyl diisocyanate; polyphenylene polymethylene polyisocyanate (PMDI) (also known as polymeric PMDI); mixtures of MDI and PMDI; mixtures of PMDI and TDI; ethylene diisocyanate; propylene-1,2-diisocyanate; trimethylene diisocyanate; butylenes diisocyanate; bitolylene diisocyanate; tolidine diisocyanate; tetramethylene-1,2-diisocyanate; tetramethylene-1,3-diisocyanate; tetramethylene-1,4-diisocyanate; pentamethylene diisocyanate; 1,6-hexamethylene diisocyanate (HDI); octamethylene diisocyanate; decamethylene diisocyanate; 2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylene diisocyanate; dodecane-1,12-diisocyanate; dicyclohexylmethane diisocyanate; cyclobutane-1,3-diisocyanate; cyclohexane-1,2-diisocyanate; cyclohexane-1,3-diisocyanate; cyclohexane-1,4-diisocyanate; diethylidene diisocyanate; methylcyclohexylene diisocyanate (HTDI); 2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane diisocyanate; 4,4′-dicyclohexyl diisocyanate; 2,4′-dicyclohexyl diisocyanate; 1,3,5-cyclohexane triisocyanate; isocyanatomethylcyclohexane isocyanate; 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane; isocyanatoethylcyclohexane isocyanate; bis(isocyanatomethyl)-cyclohexane diisocyanate; 4,4′-bis(isocyanatomethyl)dicyclohexane; 2,4′-bis(isocyanatomethyl)dicyclohexane; isophorone diisocyanate (IPDI); dimeryl diisocyanate, dodecane-1,12-diisocyanate, 1,10-decamethylene diisocyanate, cyclohexylene-1,2-diisocyanate, 1,10-decamethylene diisocyanate, 1-chlorobenzene-2,4-diisocyanate, furfurylidene diisocyanate, 2,4,4-trimethyl hexamethylene diisocyanate, 2,2,4-trimethyl hexamethylene diisocyanate, dodecamethylene diisocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,3-cyclobutane diisocyanate, 1,4-cyclohexane diisocyanate, 4,4′-methylenebis(cyclohexyl isocyanate), 4,4′-methylenebis-(phenyl isocyanate), 1-methyl-2,4-cyclohexane diisocyanate, 1-methyl-2,6-cyclohexane diisocyanate, 1,3-bis (isocyanato-methyl)cyclohexane, 1,6-diisocyanato-2,2,4,4-, tetramethyl-hexane, 1,6-diisocyanato-2,4,4-tetra-trimethylhexane, trans-cyclohexane-1,4-diisocyanate, 3-isocyanato-methyl-3,5,5-trimethylcyclo-hexyl isocyanate, 1-isocyanato -3,3,5-trimethyl-5-isocyanatomethylcyclohexane, cyclohexyl isocyanate, dicyclohexylmethane 4,4′-diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, m-phenylene diisocyanate, m-xylylene diisocyanate, m-tetramethylxylylene diisocyanate, p-phenylene diisocyanate, p,p′-biphenyl diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, 3,3′-dimethoxy-4,4′-biphenylene diisocyanate, 3,3′-diphenyl-4,4′-biphenylene diisocyanate, 4,4′-biphenylene diisocyanate, 3,3′-dichloro-4,4′-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 4-chloro-1, 3-phenylene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, metaxylene diisocyanate, 2,4-toluene diisocyanate, 2,4′-diphenylmethane diisocyanate, 2,4-chlorophenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, p,p′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2-diphenylpropane-4,4′-diisocyanate, 4,4′-toluidine diisocyanate, dianidine diisocyanate, 4,4′-diphenyl ether diisocyanate, 1,3-xylylene diisocyanate, 1,4-naphthylene diisocyanate, azobenzene-4,4′-diisocyanate, diphenyl sulfone-4,4′-diisocyanate, triphenylmethane 4,4′,4″-triisocyanate, isocyanatoethyl methacrylate, 3-isopropenyl α,α-dimethylbenzyl-isocyanate, dichlorohexamethylene diisocyanate, ω,ω-diisocyanato-1,4-diethylbenzene, polymethylene polyphenylene polyisocyanate, isocyanurate modified compounds, and carbodiimide modified compounds, as well as biuret modified compounds of the above polyisocyanates.

These isocyanates may be used either alone or in combination. These combination isocyanates include triisocyanates, such as biuret of hexamethylene diisocyanate and triphenylmethane triisocyanates, and polyisocyanates, such as polymeric diphenylmethane diisocyanate.triisocyanate of HDI; triisocyanate of 2,2,4-trimethyl-1,6-hexane diisocyanate (TMDI); 4,4′-dicyclohexylmethane diisocyanate (H₁₂MDI); 2,4-hexahydrotoluene diisocyanate; 2,6-hexahydrotoluene diisocyanate; 1,2-, 1,3-, and 1,4-phenylene diisocyanate; aromatic aliphatic isocyanate, such as 1,2-, 1,3-, and 1,4-xylene diisocyanate; meta-tetramethyixylene diisocyanate (m-TMXDI); para-tetramethylxylene tetramethylxylene diisocyanate (p-TMXDI); trimerized isocyanurate of any polyisocyanate, such as isocyanurate of toluene diisocyanate, trimer of diphenylmethane diisocyanate, trimer of tetramethylxylene diisocyanate, isocyanurate of hexamethylene diisocyanate, and mixtures thereof, dimerized uretdione of any polyisocyanate, such as uretdione of toluene diisocyanate, uretdione of hexamethylene diisocyanate, and mixtures thereof; modified polyisocyanate derived from the above isocyanates and polyisocyanates; and mixtures thereof.

Of the isocyanates, 2,2′-, 2,4′-, and 4,4′-diphenylmethane diisocyanate (MDI); 3,3′-dimethyl-4,4′-biphenylene diisocyanate (TODI); toluene diisocyanate (TDI); para-phenylene diisocyanate (PPDI); meta-phenylene diisocyanate (MPDI); and polyphenylene polymethylene polyisocyanate (PMDI) are preferred, with toluene diisocyanate (TDI) being especially preferred.

Any polyol now known or hereafter developed is suitable for use according to the invention. Polyols suitable for use in the present invention include, but are not limited to, polyester polyols, polyether polyols, polycarbonate polyols and polydiene polyols such as polybutadiene polyols. Suitable polyether polyols include polytetramethylene ether glycol (PTMEG); poly(oxypropylene) glycol; and polybutadiene glycol. Suitable polyester polyols include polyethylene adipate glycol; polyethylene propylene adipate glycol; and polybutylene adipate glycol. Suitable polylactone polyols include diethylene glycol initiated caprolactone; 1,4-butanediol initiated caprolactone; trimethylol propane initiated caprolactone; and neopentyl glycol initiated caprolactone. The preferred polyols are polytetramethylene ether glycol; polyethylene adipate glycol; polybutylene adipate glycol; and diethylene glycol initiated caprolactone. The most preferred polyol is polytetramethylene ether glycol (PTMEG). Like urethane elastomers made with other ether polyols, urethane elastomers made with PTMEG exhibit good hydrolytic stability and good tensile strength. Hydrolytic stability allows for a golf ball product that is substantially impervious to the effects of moisture. Thus, a golf ball made with a polyurethane system that has an ether glycol for the polyol component will have a longer shelf life, i.e., retains physical properties under prolonged humid conditions.

Any polyamine available to one of ordinary skill in the polyurethane art is suitable for use according to the invention. Polyamines suitable for use in the compositions of the present invention include, but are not limited to amine-terminated compounds selected from amine-terminated hydrocarbons, amine-terminated polyethers, amine-terminated polyesters, amine-terminated polycaprolactones, amine-terminated polycarbonates, amine-terminated polyamides, and mixtures thereof. The amine-terminated compound may be a polyether amine selected from polytetramethylene ether diamines, polyoxypropylene diamines, poly(ethylene oxide capped oxypropylene) ether diamines, triethyleneglycoldiamines, propylene oxide-based triamines, trimethylolpropane-based triamines, glycerin-based triamines, and mixtures thereof.

The diisocyanate and polyol or polyamine components may be combined to form a prepolymer prior to reaction with a chain extender or curing agent. Any such prepolymer combination is suitable for use in the present invention.

One preferred prepolymer is derived from toluene diisocyanate and polypropylene glycol. Such polypropylene glycol terminated toluene diisocyanate prepolymers are available from Uniroyal Chemical Company of Middlebury, Conn., under the trade name ADIPRENE® LFG963A and LFG640D. Most preferred prepolymers are the polytetramethylene ether glycol /toluene diisocyanate prepolymers including those available from Uniroyal Chemical Company of Middlebury, Conn., under the trade name ADIPRENE® LF930A, LF950A, LF601D, and LF751D.

In one embodiment, the number of free NCO groups in the urethane or urea prepolymer may be less than about 14 percent. Preferably the urethane or urea prepolymer has from about 3 percent to about 11 percent, more preferably from about 4 to about 9.5 percent, and even more preferably from about 3 percent to about 9 percent, free NCO on an equivalent weight basis.

Polyol chain extenders or curing agents may be primary, secondary, or tertiary polyols. Non-limiting examples of monomers of these polyols include: trimethylolpropane (TMP), ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, propylene glycol, dipropylene glycol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-pentanediol, 2,3-pentanediol, 2,5-hexanediol, 2,4-hexanediol, 2-ethyl-1,3-hexanediol, cyclohexanediol, and 2-ethyl-2-(hydroxymethyl)-1,3-propanediol.

Diamines and other suitable polyamines may be added to the compositions of the present invention to function as chain extenders or curing agents. These include primary, secondary and tertiary amines having two or more amines as functional groups. Exemplary diamines include aliphatic diamines, such as tetramethylenediamine, pentamethylenediamine, hexamethylenediamine; alicyclic diamines, such as 3,3′-dimethyl-4,4′-diamino-dicyclohexyl methane; or aromatic diamines, such as diethyl-2,4-toluenediamine-4,4″-methylenebis-(3-chloro,2,6-diethyl)-aniline (available from Air Products and Chemicals Inc., of Allentown, Pa., under the trade name LONZACURE®), 3,3′-dichlorobenzidene; 3,3′-dichloro-4,4′-diaminodiphenyl methane (MOCA); N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine, 3,5-dimethylthio-2,4-toluenediamine; 3,5-dimethylthio-2,6-toluenediamine; N,N′-dialkyldiamino diphenyl methane; trimethylene-glycol-di-p-aminobenzoate; polytetramethyleneoxide-di-p-aminobenzoate, 4,4′-methylene bis-2-chloroaniline, 2,2′,3,3′-tetrachloro-4,4′-diamino- phenyl methane, p,p′-methylenedianiline, p-phenylenediamine or 4,4′-diaminodiphenyl; and 2,4,6-tris(dimethylaminomethyl) phenol.

Depending on their chemical structure, curing agents may be slow- or fast-reacting polyamines or polyols. As described in U.S. Pat. Nos. 6,793,864, 6,719,646 and U.S. Patent Publication No. 2004/0201133 A1, (the contents of all of which are hereby incorporated herein by reference), slow-reacting polyamines are diamines having amine groups that are sterically and/or electronically hindered by electron withdrawing groups or bulky groups situated proximate to the amine reaction sites. The spacing of the amine reaction sites will also affect the reactivity speed of the polyamines.

Suitable curatives for use in the present invention are selected from the slow-reacting polyamine group include, but are not limited to, 3,5-dimethylthio-2,4-toluenediamine; 3,5-dimethylthio-2,6-toluenediamine; N,N′-dialkyldiamino diphenyl methane; trimethylene-glycol-di-p-aminobenzoate; polytetramethyleneoxide-di-p-aminobenzoate, and mixtures thereof. Of these, 3,5-dimethylthio-2,4-toluenediamine and 3, 5-dimethylthio-2,6-toluenediamine are isomers and are sold under the trade name ETHACURE® 300 by Ethyl Corporation. Trimethylene glycol-di-p-aminobenzoate is sold under the trade name POLACURE 740M and polytetramethyleneoxide-di-p-aminobenzoates are sold under the trade name POLAMINES by Polaroid Corporation. N,N′-dialkyldiamino diphenyl methane is sold under the trade name UNILINK® by UOP.

Also included as a curing agent for use in the polyurethane or polyurea compositions are the family of dicyandiamides as described in U.S. Pat. No. 7,879,968 filed by Kim et al., the entire contents of which are hereby incorporated by reference.

In addition to discrete thermoplastic or thermoset materials, it also is possible to modify thermoplastic polyurethane or polyurea composition by introducing materials in the composition that undergo subsequent curing after molding the thermoplastic to provide properties similar to those of a theitnoset. For example, Kim in U.S. Pat. No. 6,924,337, the entire contents of which are hereby incorporated by reference, discloses a thermoplastic urethane or urea composition optionally comprising chain extenders and further comprising a peroxide or peroxide mixture, which can then undergo post curing to result in a thermoset.

Also, Kim et al. in U.S. Pat. No. 6,939,924, the entire contents of which are hereby incorporated by reference, discloses a thermoplastic urethane or urea composition, optionally also comprising chain extenders, that are prepared from a diisocyanate and a modified or blocked diisocyanate which unblocks and induces further cross linking post extrusion. The modified isocyanate preferably is selected from the group consisting of: isophorone diisocyanate (IPDI)-based uretdione-type crosslinker; a combination of a uretdione adduct of IPDI and a partially e-caprolactam-modified IPDI; a combination of isocyanate adducts modified by e-caprolactam and a carboxylic acid functional group; a caprolactam-modified Desmodur diisocyanate; a Desmodur diisocyanate having a 3,5-dimethyl pyrazole modified isocyanate; or mixtures of these.

Finally, Kim et al. in U.S. Pat. No. 7,037,985 B2, the entire contents of which are hereby incorporated by reference, discloses thermoplastic urethane or urea compositions further comprising a reaction product of a nitroso compound and a diisocyanate or a polyisocyanate. The nitroso reaction product has a characteristic temperature at which it decomposes to regenerate the nitroso compound and diisocyanate or polyisocyanate. Thus, by judicious choice of the post-processing temperature, further crosslinking can be induced in the originally thermoplastic composition to provide thermoset-like properties.

Any polymer component of the golf balls of the present invention may be further modified by the addition of an impact modifier, which can include copolymers or terpolymers having a glycidyl group, hydroxyl group, maleic anhydride group or carboxylic group, collectively referred to as functionalized polymers. These copolymers and terpolymers may comprise an a-olefin. Examples of suitable α-olefins include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-petene, 3-methyl-1-pentene, 1-octene, 1-decene-, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, 1-dococene, 1-tetracocene, 1-hexacocene, 1-octacocene, and 1-triacontene. One or more of these α-olefins may be used.

Examples of suitable glycidyl groups in copolymers or terpolymers in the polymeric modifier include esters and ethers of aliphatic glycidyl, such as allylglycidylether, vinylglycidylether, glycidyl maleate and itaconatem glycidyl acrylate and methacrylate, and also alicyclic glycidyl esters and ethers, such as 2-cyclohexene-1-glycidylether, cyclohexene-4,5 diglyxidylcarboxylate, cyclohexene-4-glycidyl carobxylate, 5-norboenene-2-methyl-2-glycidyl carboxylate, and endocis-bicyclo(2,2,1)-5-heptene-2,3-diglycidyl dicarboxylate. These polymers having a glycidyl group may comprise other monomers, such as esters of unsaturated carboxylic acid, for example, alkyl(meth)acrylates or vinyl esters of unsaturated carboxylic acids. Polymers having a glycidyl group can be obtained by copolymerization or graft polymerization with homopolymers or copolymers.

Examples of suitable terpolymers having a glycidyl group include LOTADER AX8900 and AX8920, marketed by Atofina Chemicals, ELVALOY marketed by E.I. Du Pont de Nemours & Co., and REXPEARL marketed by Nippon Petrochemicals Co., Ltd. Additional examples of copolymers comprising epoxy monomers and which are suitable for use within the scope of the present invention include styrene-butadiene-styrene block copolymers in which the polybutadiene block contains epoxy group, and styrene-isoprene-styrene block copolymers in which the polyisoprene block contains epoxy. Commercially available examples of these epoxy functional copolymers include ESBS A1005, ESBS A1010, ESBS A1020, ESBS AT018, and ESBS AT019, marketed by Daicel Chemical Industries, Ltd.

Examples of polymers or terpolymers incorporating a maleic anhydride group suitable for use within the scope of the present invention include maleic anhydride-modified ethylene-propylene copolymers, maleic anhydride-modified ethylene-propylene-diene terpolymers, maleic anhydride-modified polyethylenes, maleic anhydride-modified polypropylenes, ethylene-ethylacrylate-maleic anhydride terpolymers, and maleic anhydride-indene-styrene-cumarone polymers. Examples of commercially available copolymers incorporating maleic anhydride include: BONDINE, marketed by Sumitomo Chemical Co., such as BONDINE AX8390, an ethylene-ethyl acrylate-maleic anhydride terpolymer having a combined ethylene acrylate and maleic anhydride content of 32% by weight, and BONDINE TX TX8030, an ethylene-ethyl acrylate-maleic anhydride terpolymer having a combined ethylene acrylate and maleic anhydride content of 15% by weight and a maleic anhydride content of 1% to 4% by weight; maleic anhydride-containing LOTADER 3200, 3210, 6200, 8200, 3300, 3400, 3410, 7500, 5500, 4720, and 4700, marketed by Atofina Chemicals; EXXELOR VA1803, a maleic anyhydride-modified ethylene-propylene copolymer having a maleic anyhydride content of 0.7% by weight, marketed by Exxon Chemical Co.; and KRATON FG 1901X, a maleic anhydride functionalized triblock copolymer having polystyrene endblocks and poly(ethylene/butylene) midblocks, marketed by Shell Chemical. Preferably the functional polymer component is a maleic anhydride grafted polymers preferably maleic anhydride grafted polyolefins (for example, Exxellor VA1803).

The various polymer compositions used to prepare the golf balls of the present invention may also be further modified by addition of a monomeric aliphatic and/or aromatic amide as described in copending US Publication No. 2007-0100085 Al filed on Nov. 1, 2006 in the name of Hyun Kim et al., the entire contents of which are hereby incorporated by reference.

Another particularly well-suited additive for use in the various polymer compositions used to prepare the golf balls of the present invention includes compounds having the general formula:

(R₂N)_(m)—R′—(X(O)_(n)OR_(y))_(m),

where R is hydrogen, or a C₁-C₂₀ aliphatic, cycloaliphatic or aromatic systems; R′ is a bridging group comprising one or more C₁-C₂₀ straight chain or branched aliphatic or alicyclic groups, or substituted straight chain or branched aliphatic or alicyclic groups, or aromatic group, or an oligomer of up to 12 repeating units including, but not limited to, polypeptides derived from an amino acid sequence of up to 12 amino acids; and X is C or S with the proviso that when X═C, n=1 and y=1 and when X═S, n=2 and y=1. Also, m=1-3. These materials are more fully described in U.S. Pat. No. 7,767,759 filed on Jul. 14, 2005, the entire contents of which are incorporated herein by reference. Preferably the material is selected from the group consisting of 4,4% methylene-bis-(cyclohexylamine)carbamate (commercially available from R.T. Vanderbilt Co., Norwalk CT under the tradename Diak® 4), 11-aminoundecanoicacid, 12-aminododecanoic acid, epsilon-caprolactam; omega-caprolactam, and any and all combinations thereof.

Golf balls within the scope of the present invention also can include, in suitable amounts, one or more additional ingredients generally employed in golf ball compositions. Agents provided to achieve specific functions, such as additives and stabilizers, can be present. Exemplary suitable ingredients include antioxidants, colorants, dispersants, mold releasing agents, processing aids, plasticizers, pigments, U.V. absorbers, optical brighteners, or any other additives generally employed in plastics formulation or the preparation of golf balls and any and all combinations thereof. Although not required, UV stabilizers, or photo stabilizers such as substituted hydroxphenyl benzotriazoles may be utilized in the present invention to enhance the UV stability of the final compositions. An example of a commercially available UV stabilizer is the stabilizer sold by Ciba Geigy Corporation under the tradename TINUVIN.

In addition to the material used to prepare the high specific gravity intermediate layer of the golf balls of the present invention, the various polymeric compositions used to prepare the golf balls of the present invention also can incorporate one or more fillers. Such fillers are typically in a finely divided form, for example, in a size generally less than about 20 mesh, preferably less than about 100 mesh U.S. standard size, except for fibers and flock, which are generally elongated. Filler particle size will depend upon desired effect, cost, ease of addition, and dusting considerations. The appropriate amounts of filler required will vary depending on the application but typically can be readily determined without undue experimentation.

The filler preferably is selected from the group consisting of precipitated hydrated silica, limestone, clay, talc, asbestos, barytes, glass fibers, aramid fibers, mica, calcium metasilicate, barium sulfate, zinc sulfide, lithopone, silicates, silicon carbide, diatomaceous earth, carbonates such as calcium or magnesium or barium carbonate, sulfates such as calcium or magnesium or barium sulfate, metals, including tungsten, steel, copper, cobalt or iron, metal alloys, tungsten carbide, metal oxides, metal stearates, and other particulate carbonaceous materials, and any and all combinations thereof. Preferred examples of fillers include metal oxides, such as zinc oxide and magnesium oxide. In another preferred aspect the filler comprises a continuous or non-continuous fiber. In another preferred aspect the filler comprises one or more so called nanofillers, as described in U.S. Pat. No. 6,794,447 and copending U.S. Publication No. US2004-0092336 filed on Sep. 24, 2003 and U.S. Pat. No. 7, 332,533, filed on Aug. 25, 2004, the entire contents of each of which are incorporated herein by reference.

Inorganic nanofiller material generally is made of clay, such as hydrotalcite, phyllosilicate, saponite, hectorite, beidellite, stevensite, vermiculite, halloysite, mica, montmorillonite, micafluoride, or octosilicate. To facilitate incorporation of the nanofiller material into a polymer material, either in preparing nanocomposite materials or in preparing polymer-based golf ball compositions, the clay particles generally are coated or treated by a suitable compatibilizing agent. The compatibilizing agent allows for superior linkage between the inorganic and organic material, and it also can account for the hydrophilic nature of the inorganic nanofiller material and the possibly hydrophobic nature of the polymer. Compatibilizing agents may exhibit a variety of different structures depending upon the nature of both the inorganic nanofiller material and the target matrix polymer. Non-limiting examples include hydroxy-, thiol-, amino-, epoxy-, carboxylic acid-, ester-, amide-, and siloxy-group containing compounds, oligomers or polymers. The nanofiller materials can be incorporated into the polymer either by dispersion into the particular monomer or oligomer prior to polymerization, or by melt compounding of the particles into the matrix polymer. Examples of commercial nanofillers are various Cloisite grades including 10A, 15A, 20A, 25A, 30B, and NA+ of Southern Clay Products (Gonzales, Tex.) and the Nanomer grades including 1.24TL and C.30EVA of Nanocor, Inc. (Arlington Heights, Ill.).

Nanofillers when added into a matrix polymer can be mixed in three ways. In one type of mixing there is dispersion of the aggregate structures within the matrix polymer, but on mixing no interaction of the matrix polymer with the aggregate platelet structure occurs, and thus the stacked platelet structure is essentially maintained. As used herein, this type of mixing is defined as “undispersed”.

However, if the nanofiller material is selected correctly, the matrix polymer chains can penetrate into the aggregates and separate the platelets, and thus when viewed by transmission electron microscopy or x-ray diffraction, the aggregates of platelets are expanded. At this point the nanofiller is said to be substantially evenly dispersed within and reacted into the structure of the matrix polymer. This level of expansion can occur to differing degrees. If small amounts of the matrix polymer are layered between the individual platelets then, as used herein, this type of mixing is known as “intercalation”.

In some circumstances, further penetration of the matrix polymer chains into the aggregate structure separates the platelets, and leads to a complete disruption of the platelet's stacked structure in the aggregate. Thus, when viewed by transmission electron microscopy (TEM), the individual platelets are thoroughly mixed throughout the matrix polymer. As used herein, this type of mixing is known as “exfoliated”. An exfoliated nanofiller has the platelets fully dispersed throughout the polymer matrix; the platelets may be dispersed unevenly but preferably are dispersed evenly.

While not wishing to be limited to any theory, one possible explanation of the differing degrees of dispersion of such nanofillers within the matrix polymer structure is the effect of the compatibilizer surface coating on the interaction between the nanofiller platelet structure and the matrix polymer. By careful selection of the nanofiller it is possible to vary the penetration of the matrix polymer into the platelet structure of the nanofiller on mixing. Thus, the degree of interaction and intrusion of the polymer matrix into the nanofiller controls the separation and dispersion of the individual platelets of the nanofiller within the polymer matrix. This interaction of the polymer matrix and the platelet structure of the nanofiller is defined herein as the nanofiller “reacting into the structure of the polymer” and the subsequent dispersion of the platelets within the polymer matrix is defined herein as the nanofiller “being substantially evenly dispersed” within the structure of the polymer matrix.

If no compatibilizer is present on the surface of a filler such as a clay, or if the coating of the clay is attempted after its addition to the polymer matrix, then the penetration of the matrix polymer into the nanofiller is much less efficient, very little separation and dispersion of the individual clay platelets occurs within the matrix polymer.

Physical properties of the polymer will change with the addition of nanofiller. The physical properties of the polymer are expected to improve even more as the nanofiller is dispersed into the polymer matrix to form a nanocomposite.

Materials incorporating nanofiller materials can provide these property improvements at much lower densities than those incorporating conventional fillers. For example, a nylon-6 nanocomposite material manufactured by RTP Corporation of Wichita, Kans., uses a 3% to 5% clay loading and has a tensile strength of 11,800 psi and a specific gravity of 1.14, while a conventional 30% mineral-filled material has a tensile strength of 8,000 psi and a specific gravity of 1.36. Using nanocomposite materials with lower inorganic materials loadings than conventional fillers provides the same properties, and this allows products comprising nanocomposite fillers to be lighter than those with conventional fillers, while maintaining those same properties.

Nanocomposite materials are materials incorporating up to about 20%, or from about 0.1% to about 20%, preferably from about 0.1% to about 15%, and most preferably from about 0.1% to about 10% of nanofiller reacted into and substantially dispersed through intercalation or exfoliation into the structure of an organic material, such as a polymer, to provide strength, temperature resistance, and other property improvements to the resulting composite. Descriptions of particular nanocomposite materials and their manufacture can be found in U.S. Pat. No. 5,962,553 to Ellsworth, U.S. Pat. No. 5,385,776 to Maxfield et al., and U.S. Pat. No. 4,894,411 to Okada et al. Examples of nanocomposite materials currently marketed include M1030D, manufactured by Unitika Limited, of Osaka, Japan, and 1015C2, manufactured by UBE America of New York, N.Y.

When nanocomposites are blended with other polymer systems, the nanocomposite may be considered a type of nanofiller concentrate. However, a nanofiller concentrate may be more generally a polymer into which nanofiller is mixed; a nanofiller concentrate does not require that the nanofiller has reacted and/or dispersed evenly into the carrier polymer.

The nanofiller material is added in an amount up to about 20 wt %, from about 0.1% to about 20%, preferably from about 0.1% to about 15%, and most preferably from about 0.1% to about 10% by weight (based on the final weight of the polymer matrix material) of nanofiller reacted into and substantially dispersed through intercalation or exfoliation into the structure of the polymer matrix.

In an especially preferred aspect, a nanofiller additive component in the golf ball of the present invention is surface modified with a compatibilizing agent comprising the earlier described compounds having the general formula:

(R₂N)_(m)—R′—(X(O)_(n)OR_(y))_(m),

Preferably the material is selected from the group consisting of 4,4′-methylene-bis-(cyclohexylamine)carbamate (commercially available from R.T. Vanderbilt Co., Norwalk CT under the tradename DIAKO 4), 11-aminoundecanoicacid, 12-aminododecanoic acid, epsilon-caprolactam; omega-caprolactam, and any and all combinations thereof.

A most preferred aspect would be a filler comprising a nanofiller clay material surface modified with an amino acid including 12-aminododecanoic acid. Such fillers are available from Nanonocor Co. under the tradename Nanomer 1.24TL.

The filler can be blended in variable effective amounts, such as amounts of greater than 0 to at least about 80 parts, and more typically from about 10 parts to about 80 parts, by weight per 100 parts by weight of the base rubber. If desired, the rubber composition can additionally contain effective amounts of a plasticizer, an antioxidant, and any other additives generally used to make golf balls.

The various formulations for the core intermediate layer and/or outer cover layer may be produced by any generally known method, such as dry blending, melt-mixing, or combination of those, to achieve a good dispersive mixing, distributive mixing, or both. Examples of melt-mixing are roll-mill; internal mixer, such as injection molding, single-screw extruder, twin-screw extruder; or any combination of those The feed to the injection mold may be blended manually or mechanically prior to the addition to the injection molder feed hopper.

In one embodiment, finished golf balls may be prepared by initially positioning the solid, preformed cellular core in an injection-molding cavity, followed by uniform injection of the high specific gravity intermediate layer composition and then the cover layer composition sequentially over the core to produce golf balls of the required diameter.

Alternatively, the intermediate layers and/or outer cover layer may also be formed around the core by first forming half shells by injection molding followed by compression molding the half shells about the the solid, preformed cellular core to form the final ball.

It is also contemplated to introduce a foamable cellular core material precursor within a hollow spherical intermediate layer and subsequently foaming that material in situ.

The intermediate layers and/or outer cover layer may also be formed around the the solid, preformed cellular core using compression molding. Cover materials for compression molding may also be extruded or blended resins or castable resins such as thermoset polyurethane or thermoset polyurea.

The golf ball of the present invention comprise from 0 to 6, preferably from 0 to 5, more preferably from about 1 to about 4, most preferably from about 1 to about 3 intermediate layer(s).

The one or more intermediate layers of the golf balls have a thickness of from about 0.010 to about 0.400, preferably from about 0.020 to about 0.200 and most preferably from about 0.030 to about 0.100 inches.

The one or more intermediate layers of the golf balls also have a Shore D hardness as measured on the ball of greater than about 25, preferably greater than about 40, and most preferably greater than about 50 Shore D units.

The one or more intermediate layers of the golf balls also have a high specific gravity of greater than or equal to 1.05, preferably greater than or equal to 1.10, more preferably greater than or equal to 1.12, and even more preferably greater than or equal to 1.15.

The one or more intermediate layers of the golf balls also have a density increasing filler concentration of greater than about 1, preferably greater than about 5, and most preferably greater than about 8 pph.

The high specific gravity material used to fot the one or more intermediate layers of the golf balls of the present invention has a viscosity as measured using a Dynamic Mechanical Analyzer (DMA) and ASTM D4440 at 200° C. of less than about 5,000 Pa-sec, preferably less than about 3,000 Pa-sec, more preferably less than about 2,000 Pa-sec and even more preferably less than about 1,000 Pa-sec.

The high specific gravity material used to form the one or more intermediate layers of the golf balls also has a storage modulus (G′) as measured using a Dynamic Mechanical Analyzer (DMA) and ASTM D4065, at 25° C., and 1 Hz, of greater than about 1×10⁷ dyn/cm², preferably greater than about 1.5×10⁷ dyn/cm², more preferably greater than about 1×10⁸ dyn/cm², and most preferably greater than about 2×10⁸ dyn/cm² .

The outer cover layer of the balls may have a thickness of from about 0.015 to about 0.100, preferably from about 0.020 to about 0.080, more preferably from about 0.025 to about 0.060 inches.

The outer cover layer the balls may also have a Shore D hardness as measured on the ball of from about 30 to about 75, preferably from 38 to about 68 and most preferably from about 40 to about 65.

The low specific gravity cores of the golf balls of the present invention have a PGA compression of less than about 100, preferably less than about 75, and most preferably less than about 50.

The low specific gravity cores of the golf balls of the present invention have a density of from about 0.2 to about 1.04 g/cm³, preferably of from about 0.4 to about 1 g/cm³, more preferably of from about 0.5 to about 0.9 g/cm³, even more preferably of from about 0.6 to about 0.8 g/cm³.

The low specific gravity cores of the golf balls of the present invention have a specific gravity of less than 1.05, preferably less than or equal to 1.00, more preferably less than or equal to 0.90, and even more preferably less than or equal to 0.80.

If prepared from a closed cell foam, the low specific gravity foamed cores of the golf balls of the present invention have a closed cell content of greater than or equal to 70% or less, preferably greater than or equal 80%, more preferably greater than or equal 90%, even more preferably greater than or equal 95%, still more preferably greater than or equal 98%, most preferably greater than or equal 99%, as measured according to according ASTM D2856-94.

The low specific gravity cores of the golf balls of the present invention have a coefficient of restitution, COR, of less than about 0.8 preferably less than 0.75 about and most preferably less than about 0.7

The foamed or cork core of the golf balls of the present invention may have a diameter of from about 0.5 to about 1.62, preferably from about 0.7 to about 1.60, more preferably from about 0.9 to about 1.58, yet more preferably from about 1.20 to about 1.54, and even more preferably from about 1.40 to about 1.50 in.

More specifically, for a three piece golf ball consisting of a core, a intermediate layer, and a cover, the diameter of the foamed or cork core is most preferably greater than or equal to 1.41 inches in diameter.

More specifically, for a four piece golf ball (consisting of a core, an inner intermediate layer, an outer intermediate layer, and a cover wherein the inner intermediate layer is encased by an outer intermediate layer) the diameter of the core is most preferably greater than or equal to 1.00 inches in diameter.

More specifically, for a five piece golf ball (consisting of an inner core, an inner intermediate layer, an intermediate intermediate layer, an outer intermediate layer, and a cover) the diameter of the core is most preferably greater than or equal to 1.00 inches in diameter.

The COR of the golf balls of the present invention may be greater than about 0.700, preferably greater than about 0.730, more preferably greater than 0.750, most preferably greater than 0.775, and especially greater than 0.800 at 125 ft/sec inbound velocity.

The shear cut resistance of the golf balls of the present invention is less than about 4, preferably less than about 3, even more preferably less than about 2.

The various test properties which may be used to measure the properties of the golf balls of the present invention are described below including any test methods as defined below.

Core or ball diameter may be determined by using standard linear calipers or size gauge.

Compression may be measured by applying a spring-loaded force to the golf ball center, golf ball core, or the golf ball to be examined, with a manual instrument (an “Atti gauge”) manufactured by the Atti Engineering Company of Union City, N.J. This machine, equipped with a Federal Dial Gauge, Model D81-C, employs a calibrated spring under a known load. The sphere to be tested is forced a distance of 0.2 inch (5 mm) against this spring. If the spring, in turn, compresses 0.2 inch, the compression is rated at 100; if the spring compresses 0.1 inch, the compression value is rated as 0. Thus more compressible, softer materials will have lower Atti gauge values than harder, less compressible materials. Compression measured with this instrument is also referred to as PGA compression. The approximate relationship that exists between Atti or PGA compression and Riehle compression can be expressed as:

(Atti or PGA compression)=(160-Riehle Compression).

Thus, a Riehle compression of 100 would be the same as an Atti compression of 60.

COR may be measured using a golf ball or golf ball subassembly, air cannon, and a stationary steel plate. The steel plate provides an impact surface weighing about 100 pounds or about 45 kilograms. A pair of ballistic light screens, which measure ball velocity, are spaced apart and located between the air cannon and the steel plate. The ball is fired from the air cannon toward the steel plate over a range of test velocities from 50 ft/s to 180 ft/sec (for the tests used herein the velocity was 125 ft/sec). As the ball travels toward the steel plate, it activates each light screen so that the time at each light screen is measured. This provides an incoming time period proportional to the ball's incoming velocity. The ball impacts the steel plate and rebounds though the light screens, which again measure the time period required to transit between the light screens. This provides an outgoing transit time period proportional to the ball's outgoing velocity. The coefficient of restitution can be calculated by the ratio of the outgoing transit time period to the incoming transit time period, COR=T_(out)/T_(in).

A “Mooney” viscosity is a unit used to measure the plasticity of raw or unvulcanized rubber. The plasticity in a Mooney unit is equal to the torque, measured on an arbitrary scale, on a disk in a vessel that contains rubber at a temperature of 100° C. and rotates at two revolutions per minute. The measurement of Mooney viscosity is defined according to ASTM D-1646.

Shore D hardness may be measured in accordance with ASTM Test D2240.

Melt flow index (MFI, 12) may be measured in accordance with ASTM D-1238, Condition 230° C/2.16 kg.

Tensile Strength and Tensile Elongation were measured with ASTM D-638.

Flexural modulus and flexural strength were measured using ASTM standard D-790.

Shear cut resistance may be determined by examining the balls after they were impacted by a pitching wedge at controlled speed, classifying each numerically from 1 (excellent) to 5 (poor), and averaging the results for a given ball type. Three samples of each Example may be used for this testing. Each ball is hit twice, to collect two impact data points per ball. Then, each ball is assigned two numerical scores-one for each impact-from 1 (no visible damage) to 5 (substantial material displaced). These scores may be then averaged for each Example to produce the shear resistance numbers. These numbers may be then directly compared with the corresponding number for a commercially available ball, having a similar construction including the same core and intermediate layer composition and cover thickness for comparison purposes.

Impact durability may be tested with an endurance test machine. The endurance test machine is designed to impart repetitive deformation to a golf ball similar to a driver impact. The test machine consists of an arm and impact plate or club face that both rotate to a speed that generates ball speeds of approximately 155-160mph. Ball speed is measured with two light sensors located 15.5″ from impact location and are 11″ apart. The ball is stopped by a net and if a test sample is not cracked will continue to cycle through the machine for additional impacts. For golf balls, if zero failures occur through in excess of 100 impacts per ball than minimal field failures will occur. For layers adjacent to the outer cover, fewer impacts are required since the cover typically “protects” the inner components of the golf ball.

Golf ball Sound Pressure Level, S, in decibels (dB) and Frequency in hertz (Hz) may be measured by dropping the ball from a height of 113 in onto a marble (“starnet crystal pink”) stage of at least 12″ square and 4.25 inches in thickness. The sound of the resulting impact is captured by a microphone positioned at a fixed proximity of 12 inches, and at an angle of 30 degrees from horizontal, from the impact position and resolved by software transformation into an intensity in db and a frequency in Hz. Data collection is done as follows:

Microphone data is collected using a laptop PC with a sound card. An A-weighting filter is applied to the analog signal from the microphone. This signal is then digitally sampled at 44.1 KHz by the laptop data acquisition system for further processing and analysis. Data Analysis was done as follows:

The data analysis is split into two processes:

a. Time series analysis that generates the root mean square (rms) sound pressure level (SPL) for each ball impact sound.

-   -   i. An rms SPL from a reference calibration signal is generated         in the same manner as the ball data.     -   ii. The overall SPL (in decibels) is calculated from the         reference signal for each ball impact sound.     -   iii. The median SPL is recorded based on 3 impact tests.

b. Spectral analyses for each ball impact sound

-   -   i. Fourier and Autoregressive spectral estimation techniques are         employed to create power spectra.     -   ii. The frequencies (in cycles/sec - Hz) from highest level         peaks representing the most active sound producing vibration         modes of each ball are identified.

In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims. 

We claim:
 1. A golf ball comprising; I. a core having a specific gravity of less than 1.05; II. one or more intermediate layers having a specific gravity of greater than or equal to 1.05; and III. an outer cover layer.
 2. The golf ball of claim 1 wherein; I. said core has a specific gravity of less than or equal to 1.00; II. said one or more intermediate layers a specific gravity of greater than or equal to 1.20.
 3. The golf ball of claim 1 wherein; I. said core has a specific gravity of less than or equal to 0.95; II. said one or more intermediate layers has a specific gravity of greater than or equal to 1.30.
 4. The golf ball of claim 3 wherein; I. said core has a specific gravity of less than or equal to 0.85 and comprises a material selected from the group consisting of; a) natural cork; b) a closed cell foam having a density of from about 0.2 to about 1.04 g/cm³ and a closed cell content of greater than or equal 70%, as measured according to according ASTM D2856-94; and c) any and all combination of a) and b); and II. said one or more intermediate layers have a specific gravity of greater than or equal to 1.50 and comprises a polyalkenamer having a) a trans-content of from about 40 to about 95%; b) a cis- content of from about 5 to about 60%; c) a melting point of greater than about 15° C.; d) a viscosity of less than about 5,000 Pa-sec as measured using a Dynamic Mechanical Analyzer (DMA) and ASTM D4440 at 200° C.; and e) a storage modulus (G) of greater than about 1×10⁷ dyn/cm² as measured using a Dynamic Mechanical Analyzer (DMA) and ASTM D4065, at 25° C., and 1 Hz; and III. said outer cover layer comprises a polymer selected from the group consisting of ionomers, thermoset polyureas, thermoset polyurethanes, thermoplastic polyurethanes, thermoplastic polyureas , a multicomponent blend composition (“MCBC”) comprising (A) a block copolymer; and (B) one or more acidic polymers; and (C) one or more basic metal salts present in an amount to neutralize at greater than or equal to about 30 percent of the acid groups of Component (B), and any and all combinations thereof.
 5. The golf ball of claim 4 wherein said one or more intermediate layers further comprises a peptizer selected from the group consisting of an organic sulfur compound, a metal salt of an organic sulfur compound, a non-metal salt of an organic sulfur compound, and any and all combinations thereof.
 6. A three piece golf ball consisting essentially of; I. a core having a specific gravity of less than or equal to 0.85 and comprising a material selected from the group consisting of; a) natural cork; b) a closed cell foam having a density of from about 0.2 to about 1.04 g/cm³ and a closed cell content of greater than or equal 70%, as measured according to according ASTM D2856-94; and c) any and all combination of a) and b); and II. an intermediate layer having a thickness of from about 0.010 to about 0.400 inches and a Shore D hardness as measured on the ball of greater than about 25 and a specific gravity of greater than or equal to 1.20, and comprising a polyalkenamer having; a) a trans-content of from about 40 to about 95%; b) a cis- content of from about 5 to about 60%; c) a melting point of greater than about 15° C.; d) a viscosity of less than about 5,000 Pa-sec as measured using a Dynamic Mechanical Analyzer (DMA) and ASTM D4440 at 200° C.; and e) a storage modulus (G′) of greater than about 1×10⁷ dyn/cm² as measured using a Dynamic Mechanical Analyzer (DMA) and ASTM D4065, at 25° C., and 1 Hz; and III. an outer cover layer having a thickness of from about 0.015 to about 0.100 inches a Shore D hardness as measured on the ball of from about 30 to about 75, said outer cover layer comprising a polymer selected from the group consisting of ionomers, thermoset polyureas, thermoset polyurethanes, thermoplastic polyurethanes, thermoplastic polyureas , a multicomponent blend composition (“MCBC”) comprising (A) a block copolymer; and (B) one or more acidic polymers; and (C) one or more basic metal salts present in an amount to neutralize at greater than or equal to about 30 percent of the acid groups of Component (B), and any and all combinations thereof.
 7. The three piece golf ball of claim 6 wherein said one or more intermediate layers further comprises a peptizer selected from the group consisting of an organic sulfur compound, a metal salt of an organic sulfur compound, a non-metal salt of an organic sulfur compound, and any and all combinations thereof.
 8. A four piece golf ball consisting essentially of; I. a core having a specific gravity of less than or equal to 0.85 and comprising a material selected from the group consisting of; a) natural cork; b) a closed cell foam having a density of from about 0,2 to about 1.04 g/cm³ and a closed cell content of greater than or equal 70%, as measured according to according ASTM D2856-94; and c) any and all combination of a) and b); and; II. an inner intermediate layer having a thickness of from about 0.010 to about 0.400 inches and a Shore D hardness as measured on the ball of greater than about 25, and a specific gravity of greater than or equal to 1.20, comprising a polyalkenamer having; a) a trans-content of from about 40 to about 95%; b) a cis- content of from about 5 to about 60%; c) a melting point of greater than about 15° C.; d) a viscosity of less than about 5,000 Pa-sec as measured using a Dynamic Mechanical Analyzer (DMA) and ASTM D4440 at 200° C.; and e) a storage modulus (G′) of greater than about 1×10⁷ dyn/cm² as measured using a Dynamic Mechanical Analyzer (DMA) and ASTM D4065, at 25° C., and 1 Hz; and III. an outer intermediate layer having a thickness of from about 0.010 to about 0.400 inches and a Shore D hardness as measured on the ball of greater than about 25; and IV. an outer cover layer having a thickness of from about 0.015 to about 0.100 inches and a Shore D hardness as measured on the ball of from about 30 to about 75, and comprising a polymer selected from the group consisting of ionomers, thermoset polyureas, thermoset polyurethanes, thermoplastic polyurethanes, thermoplastic polyureas , a multicomponent blend composition (“MCBC”) comprising (A) a block copolymer; and (B) one or more acidic polymers; and (C) one or more basic metal salts present in an amount to neutralize at greater than or equal to about 30 percent of the acid groups of Component (B), and any and all combinations thereof.
 9. The golf ball of claim 8 wherein said one or more intermediate layers further comprises a peptizer selected from the group consisting of an organic sulfur compound, a metal salt of an organic sulfur compound, a non-metal salt of an organic sulfur compound, and any and all combinations thereof.
 10. A five piece golf ball consisting essentially of; I. a core having a specific gravity of less than or equal to 0.85 and comprising a material selected from the group consisting of; a) natural cork; b) a closed cell foam having a density of from about 0.2 to about 1.04 g/cm³ and a closed cell content of greater than or equal 70%, as measured according to according ASTM D2856-94; and c) any and all combination of a) and b); and; II. an inner intermediate layer having a thickness of from about 0.010 to about 0.400 inches and a Shore D hardness as measured on the ball of greater than about 25, and a specific gravity of greater than or equal to 1.20, and comprising a polyalkenamer having; a) a trans-content of from about 40 to about 95%; b) a cis- content of from about 5 to about 60%; c) a melting point of greater than about 15° C.; d) a viscosity of less than about 5,000 Pa-sec as measured using a Dynamic Mechanical Analyzer (DMA) and ASTM D4440 at 200° C.; and e) a storage modulus (G′) of greater than about 1×10⁷ dyn/cm² as measured using a Dynamic Mechanical Analyzer (DMA) and ASTM D4065, at 25° C., and 1 Hz; and; III. an intermediate intermediate layer having a thickness of from about 0.010 to about 0.400 inches and a Shore D hardness as measured on the ball of greater than about 25; IV. an outer intermediate layer having a thickness of from about 0.010 to about 0.400 inches and a Shore D hardness as measured on the ball of greater than about 25; and V. an outer cover layer having a thickness of from about 0.015 to about 0.100 inches and a Shore D hardness as measured on the ball of from about 30 to about 75, and wherein said outer intermediate layer comprises a polymer selected from the group consisting of ionomers, thermoset polyureas, thermoset polyurethanes, thermoplastic polyurethanes, thermoplastic polyureas , a multicomponent blend composition (“MCBC”) comprising (A) a block copolymer; and (B) one or more acidic polymers; and (C) one or more basic metal salts present in an amount to neutralize at greater than or equal to about 30 percent of the acid groups of Component (B), and any and all combinations thereof.
 11. The golf ball of claim 10 wherein said one or more intermediate layers further comprises a peptizer selected from the group consisting of an organic sulfur compound, a metal salt of an organic sulfur compound, a non-metal salt of an organic sulfur compound, and any and all combinations thereof 